build: Raise gjs dependency to ensure ES6 classes
Without ES6 (e.g. gjs-1.48.x) gnome-weather fails to run since commit d23c49c0 with:
Gjs-CRITICAL **: 16:08:50.395: JS ERROR: SyntaxError: class is a reserved identifier @ resource:///org/gnome/Weather/Application/js/app/currentLocationController.js:33 JS_EvaluateScript() failed
Update the gjs requirement in configure to ensure a new enough gjs for this.