Fix trivial Qt6 deprecations (QString::count, QColor::setNamedColor)

QString::count() (no-arg) is deprecated -> size(); QColor::setNamedColor()
is deprecated -> the QColor(QString) constructor. Both replacements are
non-deprecated on Qt5 too. Clears 2 -Wdeprecated-declarations warnings.

sources/ElementsCollection/elementscollectionwidget.cpp

@@ -830,7 +830,7 @@ void ElementsCollectionWidget::search()
 	}
 
 		//start the search when text have at least 3 letters.
-	if (text.count() < 3) {
+	if (text.size() < 3) {
 		return;
 	}