TerminalDisplay: sync the primary selection as it won't be a 3x click

We'd added a delay until the 3x click is resolved, but this meant
that if the middleclick paste happened before that timeout we'd paste
something wrong. This addresses it by also syncing as soon as we realise
that it won't be a 3x click.

CCBUG: 462338

src/terminalDisplay/TerminalDisplay.cpp

@@ -1125,6 +1125,11 @@ void TerminalDisplay::mousePressEvent(QMouseEvent *ev)
         return;
     }
 
+    if (_needCopyToX11Selection && (ev->button() != Qt::LeftButton)) {
+        copyToX11Selection();
+        _needCopyToX11Selection = false;
+    }
+
     if (_possibleTripleClick && (ev->button() == Qt::LeftButton)) {
         _needCopyToX11Selection = false;
         mouseTripleClickEvent(ev);