Issue #3417816 by Watergate: Ensure database connection information is cleaned...

Issue #3417816 by Watergate: Ensure database connection information is cleaned up properly after performing ConnectionTest

(cherry picked from commit d0fecb79)

core/tests/Drupal/Tests/Core/Database/ConnectionTest.php

@@ -982,4 +982,15 @@ public function testDeprecatedFetchModes(int $mode): void {
     $statement->setFetchMode($mode);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function tearDown(): void {
+    parent::tearDown();
+
+    // Removes the default connection added by the
+    // testFindCallerFromDebugBacktrace test.
+    Database::removeConnection('default');
+  }
+
 }