Revert "Disconnecting the database connection after testing (#49327)" (#49361)

This reverts commit 2f65457.

Author: driesvints

src/Illuminate/Foundation/Testing/DatabaseTransactions.php

@@ -33,7 +33,7 @@ public function beginDatabaseTransaction()
                 $connection->unsetEventDispatcher();
                 $connection->rollBack();
                 $connection->setEventDispatcher($dispatcher);
-                $database->purge($name);
+                $connection->disconnect();
             }
         });
     }

src/Illuminate/Foundation/Testing/RefreshDatabase.php

@@ -109,7 +109,7 @@ public function beginDatabaseTransaction()
                 $connection->unsetEventDispatcher();
                 $connection->rollBack();
                 $connection->setEventDispatcher($dispatcher);
-                $database->purge($name);
+                $connection->disconnect();
             }
         });
     }

src/Illuminate/Foundation/Testing/TestCase.php

@@ -197,12 +197,6 @@ protected function tearDown(): void
 
             ParallelTesting::callTearDownTestCaseCallbacks($this);
 
-            $database = $this->app['db'] ?? null;
-
-            foreach (array_keys($database?->getConnections() ?? []) as $name) {
-                $database->purge($name);
-            }
-
             $this->app->flush();
 
             $this->app = null;