build(dependencies): pin leaflet version (#453)

Pin leaflet version to 1.7.1

Author: mpfeil

bower.json

@@ -19,7 +19,7 @@
     "angular-wizard": "^0.10.0",
     "bootstrap-css-only": "^3.3.7",
     "angular-bootstrap": "^2.5.0",
-    "leaflet": "^1.1.0",
+    "leaflet": "1.7.1",
     "Leaflet.awesome-markers": "leaflet-awesome-markers#^2.0.2",
     "leaflet.markercluster": "1.4.1",
     "mapbox-gl-js": "https://api.mapbox.com/mapbox-gl-js/v1.13.1/mapbox-gl.js",