Make map location HTML class names consistent

We were using `map_location` in one place and
`location-map-remove-marker` in another one. We usually use dashes in
HTML class names, we don't say "location map" anywhere else.

app/assets/stylesheets/map_location.scss

@@ -1,4 +1,4 @@
-.location-map-remove-marker {
+.map-location-remove-marker {
   border-bottom: 1px dotted #cf2a0e;
   color: $delete;
   display: inline-block;