Various Plugins: Simplify return FilePath statements

Change-Id: Ia9efb86f722caca1492b577d51442f1f23b804b4
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/mcusupport/mcukitmanager.cpp

@@ -413,7 +413,7 @@ static FilePath kitDependencyPath(const Kit *kit, const QString &cmakeVariableNa
         if (configItem.key == keyName)
             return FilePath::fromUserInput(QString::fromUtf8(configItem.value));
     }
-    return FilePath();
+    return {};
 }
 
 // Kit Information