Add and apply Style/MapToHash rubocop rule

This rule was added in Rubocop 1.24.0. Applying it slightly simplifies
the code.

spec/system/admin/translatable_spec.rb

@@ -9,9 +9,9 @@ describe "Admin edit translatable records", :admin do
   let(:fields) { translatable.translated_attribute_names }
 
   let(:attributes) do
-    fields.product(%i[en es]).map do |field, locale|
+    fields.product(%i[en es]).to_h do |field, locale|
       [:"#{field}_#{locale}", text_for(field, locale)]
-    end.to_h
+    end
   end
 
   context "Add a translation" do

spec/system/translatable_spec.rb

@@ -182,9 +182,9 @@ describe "Public area translatable records" do
     before { translatable.update(attributes.merge(author: user)) }
 
     let(:attributes) do
-      translatable.translated_attribute_names.product(%i[en es]).map do |field, locale|
+      translatable.translated_attribute_names.product(%i[en es]).to_h do |field, locale|
         [:"#{field}_#{locale}", text_for(field, locale)]
-      end.to_h
+      end
     end
 
     context "Update a translation" do