Merge branch '391117-vue3-migration-mr_widget_memory_usage_spec' into 'master'

Remove Vue.extend from mr_widget_memory_usage_spec

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/117335



Merged-by: Andrew Fontaine <afontaine@gitlab.com>
Approved-by: Andrew Fontaine <afontaine@gitlab.com>
Approved-by: Ross Byrne <robyrne@gitlab.com>
Reviewed-by: Andrew Fontaine <afontaine@gitlab.com>
Co-authored-by: Artur Fedorov <afedorov@gitlab.com>