Revert "Adapt default shortcut for completion on Mac."

This reverts commit 497e5141.

I'm proved wrong by other mac installations.

src/plugins/texteditor/texteditorplugin.cpp

@@ -127,7 +127,7 @@ bool TextEditorPlugin::initialize(const QStringList &arguments, QString *errorMe
 #ifndef Q_WS_MAC
     command->setDefaultKeySequence(QKeySequence(tr("Ctrl+Space")));
 #else
-    command->setDefaultKeySequence(QKeySequence(tr("Alt+Space")));
+    command->setDefaultKeySequence(QKeySequence(tr("Meta+Space")));
 #endif
     connect(completionShortcut, SIGNAL(activated()), this, SLOT(invokeCompletion()));