Remove duplicate i18n text to remove marker

We had two different keys with the same text and were passing it as a
parameter. Since the text is the same in any case, we don't need a
parameter for it.

Note we are using the `proposals` i18n key instead of creating a new one
in a `shared` namespace one because creating a new key would mean that
we'd lose the already existing translations in Crowdin.

app/components/shared/map_location_component.rb

@@ -1,9 +1,8 @@
 class Shared::MapLocationComponent < ApplicationComponent
-  attr_reader :remove_marker_label, :investments_coordinates, :form
+  attr_reader :investments_coordinates, :form
 
-  def initialize(map_location, remove_marker_label: nil, investments_coordinates: nil, form: nil)
+  def initialize(map_location, investments_coordinates: nil, form: nil)
     @map_location = map_location
-    @remove_marker_label = remove_marker_label
     @investments_coordinates = investments_coordinates
     @form = form
   end
@@ -30,6 +29,10 @@ class Shared::MapLocationComponent < ApplicationComponent
       map_location.zoom.presence || Setting["map.zoom"]
     end
 
+    def remove_marker_label
+      t("proposals.form.map_remove_marker")
+    end
+
     def remove_marker_link_id
       "remove-marker-link-#{dom_id(map_location)}"
     end