Fix tab bar layout key handling in RTL

Summary:
Current code will, when mirrored, treat all keys like they're the left
key.

BUG: 379894

Test Plan: Ran plasma in RTL

Reviewers: #plasma, broulik

Reviewed By: #plasma, broulik

Subscribers: plasma-devel, #frameworks

Tags: #plasma, #frameworks

Differential Revision: https://phabricator.kde.org/D6480

src/declarativeimports/plasmacomponents/qml/private/TabBarLayout.qml

@@ -77,7 +77,7 @@ Item {
         if (event.key == Qt.Key_Right) {
             (priv.mirrored ? priv.goPreviousTab : priv.goNextTab)();
             event.accepted = true
-        } else if (event.key == Qt.Key_Left || priv.mirrored) {
+        } else if (event.key == Qt.Key_Left) {
             (priv.mirrored ? priv.goNextTab : priv.goPreviousTab)();
             event.accepted = true
         }