Fix formatting of HAML line

The attribute hashes can only be multi-line after commas
are specified on each line, per
https://haml.info/docs/yardoc/file.REFERENCE.html

app/views/notify/new_merge_request_email.html.haml

 %p.details
-  = html_escape(_('%{userLinkStart}%{user}%{linkEnd} created a %{mrLinkStart}merge request%{linkEnd}:')) % {
-    userLinkStart: "<a href=\"#{user_url(@merge_request.author)}\">".html_safe,
-    user: @merge_request.author_name,
-    mrLinkStart: "<a href=\"#{merge_request_url(@merge_request)}\">".html_safe,
-    linkEnd: '</a>'.html_safe
-  }
+  = html_escape(_('%{userLinkStart}%{user}%{linkEnd} created a %{mrLinkStart}merge request%{linkEnd}:')) % {userLinkStart: "<a href=\"#{user_url(@merge_request.author)}\">".html_safe,
+                                                                                                            user: @merge_request.author_name,
+                                                                                                            mrLinkStart: "<a href=\"#{merge_request_url(@merge_request)}\">".html_safe,
+                                                                                                            linkEnd: '</a>'.html_safe}
 
 %p
   .branch