Fix code that depends on incorrect inflector behavior

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/views/search/results/_commits.html.haml → app/views/search/results/_commit.html.haml

 .search-result-row
-  = render 'projects/commits/commit', project: @project, commit: commits
+  = render 'projects/commits/commit', project: @project, commit: commit

spec/mailers/notify_spec.rb

@@ -468,7 +468,7 @@ describe Notify do
         subject { Notify.note_commit_email(recipient.id, note.id) }
         it_behaves_like 'a note email'
-        it_behaves_like 'an answer to an existing thread', 'commits'
+        it_behaves_like 'an answer to an existing thread', 'commit'
         it 'has the correct subject' do
           is_expected.to have_subject /#{commit.title} \(#{commit.short_id}\)/