Remove "X-UA-Compatible" header

IE=edge is the default mode anyway
https://msdn.microsoft.com/en-us/library/jj676915(v=vs.85).aspx

app/views/layouts/registrant/application.haml

@@ -2,7 +2,6 @@
 %html{lang: I18n.locale.to_s}
   %head
     %meta{charset: "utf-8"}/
-    %meta{content: "IE=edge", "http-equiv" => "X-UA-Compatible"}/
     %meta{content: "width=device-width, initial-scale=1", name: "viewport"}/
     %meta{content: "Full stack top-level domain (TLD) management.", name: "description"}/
     %meta{content: "Gitlab LTD", name: "author"}/