docs: fix/add @return types

phpstan-baseline.php

@@ -3001,11 +3001,6 @@ $ignoreErrors[] = [
 	'count' => 11,
 	'path' => __DIR__ . '/system/Database/MySQLi/Connection.php',
 ];
-$ignoreErrors[] = [
-	'message' => '#^Method CodeIgniter\\\\Database\\\\MySQLi\\\\Connection\\:\\:_close\\(\\) should return mixed but return statement is missing\\.$#',
-	'count' => 1,
-	'path' => __DIR__ . '/system/Database/MySQLi/Connection.php',
-];
 $ignoreErrors[] = [
 	'message' => '#^Only booleans are allowed in &&, int given on the left side\\.$#',
 	'count' => 1,
@@ -3391,11 +3386,6 @@ $ignoreErrors[] = [
 	'count' => 2,
 	'path' => __DIR__ . '/system/Database/Postgre/Connection.php',
 ];
-$ignoreErrors[] = [
-	'message' => '#^Method CodeIgniter\\\\Database\\\\Postgre\\\\Connection\\:\\:_close\\(\\) should return mixed but return statement is missing\\.$#',
-	'count' => 1,
-	'path' => __DIR__ . '/system/Database/Postgre/Connection.php',
-];
 $ignoreErrors[] = [
 	'message' => '#^Method CodeIgniter\\\\Database\\\\Postgre\\\\Connection\\:\\:buildDSN\\(\\) has no return type specified\\.$#',
 	'count' => 1,
@@ -3756,11 +3746,6 @@ $ignoreErrors[] = [
 	'count' => 1,
 	'path' => __DIR__ . '/system/Database/SQLSRV/Connection.php',
 ];
-$ignoreErrors[] = [
-	'message' => '#^Method CodeIgniter\\\\Database\\\\SQLSRV\\\\Connection\\:\\:_close\\(\\) should return mixed but return statement is missing\\.$#',
-	'count' => 1,
-	'path' => __DIR__ . '/system/Database/SQLSRV/Connection.php',
-];
 $ignoreErrors[] = [
 	'message' => '#^PHPDoc type string of property CodeIgniter\\\\Database\\\\SQLSRV\\\\Connection\\:\\:\\$escapeChar is not the same as PHPDoc type array\\|string of overridden property CodeIgniter\\\\Database\\\\BaseConnection\\<resource,resource\\>\\:\\:\\$escapeChar\\.$#',
 	'count' => 1,
@@ -3951,11 +3936,6 @@ $ignoreErrors[] = [
 	'count' => 1,
 	'path' => __DIR__ . '/system/Database/SQLite3/Connection.php',
 ];
-$ignoreErrors[] = [
-	'message' => '#^Method CodeIgniter\\\\Database\\\\SQLite3\\\\Connection\\:\\:_close\\(\\) should return mixed but return statement is missing\\.$#',
-	'count' => 1,
-	'path' => __DIR__ . '/system/Database/SQLite3/Connection.php',
-];
 $ignoreErrors[] = [
 	'message' => '#^Method CodeIgniter\\\\Database\\\\SQLite3\\\\Connection\\:\\:getFieldNames\\(\\) return type has no value type specified in iterable type array\\.$#',
 	'count' => 1,
@@ -8661,11 +8641,6 @@ $ignoreErrors[] = [
 	'count' => 1,
 	'path' => __DIR__ . '/system/Test/Mock/MockConnection.php',
 ];
-$ignoreErrors[] = [
-	'message' => '#^Method CodeIgniter\\\\Test\\\\Mock\\\\MockConnection\\:\\:_close\\(\\) should return mixed but return statement is missing\\.$#',
-	'count' => 1,
-	'path' => __DIR__ . '/system/Test/Mock/MockConnection.php',
-];
 $ignoreErrors[] = [
 	'message' => '#^Method CodeIgniter\\\\Test\\\\Mock\\\\MockConnection\\:\\:_fieldData\\(\\) return type has no value type specified in iterable type array\\.$#',
 	'count' => 1,

system/Database/BaseConnection.php

@@ -479,7 +479,7 @@ abstract class BaseConnection implements ConnectionInterface
     /**
      * Platform dependent way method for closing the connection.
      *
-     * @return mixed
+     * @return void
      */
     abstract protected function _close();
 

system/Database/MySQLi/Connection.php

@@ -246,6 +246,8 @@ class Connection extends BaseConnection
 
     /**
      * Close the database connection.
+     *
+     * @return void
      */
     protected function _close()
     {

system/Database/Postgre/Connection.php

@@ -146,6 +146,8 @@ class Connection extends BaseConnection
 
     /**
      * Close the database connection.
+     *
+     * @return void
      */
     protected function _close()
     {

system/Database/SQLSRV/Connection.php

@@ -173,6 +173,8 @@ class Connection extends BaseConnection
 
     /**
      * Close the database connection.
+     *
+     * @return void
      */
     protected function _close()
     {

system/Database/SQLite3/Connection.php

@@ -110,6 +110,8 @@ class Connection extends BaseConnection
 
     /**
      * Close the database connection.
+     *
+     * @return void
      */
     protected function _close()
     {

system/Test/Mock/MockConnection.php

@@ -220,6 +220,8 @@ class MockConnection extends BaseConnection
 
     /**
      * Close the connection.
+     *
+     * @return void
      */
     protected function _close()
     {