Remove requires-input from the Network Graph form

The "Begin with the selected commit" checkbox requires the submit button
to be enabled, even if the extended SHA1 input field is blank.

app/views/projects/network/show.html.haml

@@ -2,8 +2,8 @@
 = render "head"
 .project-network
   .controls
-    = form_tag namespace_project_network_path(@project.namespace, @project, @id), method: :get, class: 'form-inline network-form js-requires-input' do |f|
-      = text_field_tag :extended_sha1, @options[:extended_sha1], placeholder: "Input an extended SHA1 syntax", class: 'search-input form-control input-mx-250 search-sha', required: true
+    = form_tag namespace_project_network_path(@project.namespace, @project, @id), method: :get, class: 'form-inline network-form' do |f|
+      = text_field_tag :extended_sha1, @options[:extended_sha1], placeholder: "Input an extended SHA1 syntax", class: 'search-input form-control input-mx-250 search-sha'
       = button_tag class: 'btn btn-success' do
         = icon('search')
       .inline.prepend-left-20