Disable password autocomplete in mirror form fill

Chrome and other browsers ignore `autocomplete=false` and
`autocomplete=off` now. We suspect that this caused the mirroring
section to expand whenever a user clicked "Expand" in the Repository
settings.

https://developers.google.com/web/fundamentals/design-and-ux/input/forms/?hl=en
recommends using `new-password` as the new field to prevent automatic
filling.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/50812

ee/app/views/projects/mirrors/pull/_authentication_method.html.haml

@@ -13,7 +13,7 @@
     .changing-auth-method= icon('spinner spin lg')
   .well-password-auth.collapse.js-well-password-auth
     = f.label :password, _("Password"), class: "label-bold"
-    = f.password_field :password, value: import_data.password, class: 'form-control'
+    = f.password_field :password, value: import_data.password, class: 'form-control', autocomplete: 'new-password'
   .well-ssh-auth.collapse.js-well-ssh-auth
     %p.js-ssh-public-key-present{ class: ('collapse' unless ssh_public_key_present) }
       = _('Here is the public SSH key that needs to be added to the remote server. For more information, please refer to the documentation.')

ee/changelogs/unreleased/sh-disable-autocomplete-mirror-password.yml

+---
+title: Disable password autocomplete in mirror form fill
+merge_request:
+author:
+type: fixed