Remove duplicate code expanding size hint of panel to fit text

QtQuickControls already does this inside Button code. This hint is meant
to be "what's the default size for a panel to be".

Change-Id: I12fd084a3d3c35b172fbff9c7d3ab5c5565a82dc

src/declarativeimports/plasmastyle/ButtonStyle.qml

@@ -111,7 +111,7 @@ QtQuickControlStyle.ButtonStyle {
             if (control.text.length == 0) {
                 height;
             } else {
-                Math.max(theme.mSize(theme.defaultFont).width*12, style.minimumWidth);
+                theme.mSize(theme.defaultFont).width*12
             }
         }