HAMLLint: Fix `TrailingWhitespace` offences

app/views/abuse_report_mailer/notify.html.haml

...doorkeeper/authorized_applications/_delete_form.html.haml

app/views/projects/_find_file_link.html.haml

app/views/projects/forks/index.html.haml

app/views/projects/merge_requests/_merge_request.html.haml

app/views/projects/merge_requests/widget/_closed.html.haml

app/views/projects/merge_requests/widget/_open.html.haml

...s/projects/merge_requests/widget/open/_archived.html.haml

...ws/projects/merge_requests/widget/open/_nothing.html.haml