Replace .attribute('src') with .element.src in specs to fix Vue 3 specs

What does this MR do and why?

Closes #481462 (closed) #481461 (closed) #481456 (closed) #481429 (closed) #481428 (closed) #481427 (closed) #481426 (closed) #481425 (closed) #481424 (closed) #481423 (closed) #481422 (closed) #481421 (closed) #481419 (closed) #481416 (closed) #481415 (closed) #483190 (closed) #483191 (closed) #483196 (closed) #481414 (closed) #481457 (closed)

Subepic: &15001

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Before	After

How to set up and validate locally

Vue2:

yarn jest ee/spec/frontend/approvals/mr_edit/free_tier_promo_spec.js spec/frontend/admin/abuse_report/components/reported_content_spec.js spec/frontend/badges/components/badge_spec.js spec/frontend/design_management/components/list/item_spec.js spec/frontend/groups/components/empty_states/subgroups_and_projects_empty_state_spec.js spec/frontend/ide/components/terminal/empty_state_spec.js spec/frontend/pages/projects/forks/new/components/app_spec.js spec/frontend/repository/components/blob_viewers/image_viewer_spec.js spec/frontend/sidebar/components/assignees/assignee_avatar_spec.js spec/frontend/sidebar/components/assignees/assignees_spec.js spec/frontend/super_sidebar/components/brand_logo_spec.js spec/frontend/vue_merge_request_widget/components/mr_widget_author_spec.js spec/frontend/vue_merge_request_widget/components/mr_widget_suggest_pipeline_spec.js spec/frontend/vue_shared/alert_details/sidebar/alert_sidebar_assignees_spec.js spec/frontend/vue_shared/components/content_viewer/viewers/image_viewer_spec.js spec/frontend/vue_shared/components/diff_viewer/viewers/image_diff_viewer_spec.js spec/frontend/vue_shared/components/diff_viewer/diff_viewer_spec.js spec/frontend/vue_shared/new_namespace/components/welcome_spec.js spec/frontend/vue_shared/new_namespace/new_namespace_page_spec.js spec/frontend/work_items/components/design_management/design_item_spec.js

Vue3:

VUE_VERSION=3 yarn jest ee/spec/frontend/approvals/mr_edit/free_tier_promo_spec.js spec/frontend/admin/abuse_report/components/reported_content_spec.js spec/frontend/badges/components/badge_spec.js spec/frontend/design_management/components/list/item_spec.js spec/frontend/groups/components/empty_states/subgroups_and_projects_empty_state_spec.js spec/frontend/ide/components/terminal/empty_state_spec.js spec/frontend/pages/projects/forks/new/components/app_spec.js spec/frontend/repository/components/blob_viewers/image_viewer_spec.js spec/frontend/sidebar/components/assignees/assignee_avatar_spec.js spec/frontend/sidebar/components/assignees/assignees_spec.js spec/frontend/super_sidebar/components/brand_logo_spec.js spec/frontend/vue_merge_request_widget/components/mr_widget_author_spec.js spec/frontend/vue_merge_request_widget/components/mr_widget_suggest_pipeline_spec.js spec/frontend/vue_shared/alert_details/sidebar/alert_sidebar_assignees_spec.js spec/frontend/vue_shared/components/content_viewer/viewers/image_viewer_spec.js spec/frontend/vue_shared/components/diff_viewer/viewers/image_diff_viewer_spec.js spec/frontend/vue_shared/components/diff_viewer/diff_viewer_spec.js spec/frontend/vue_shared/new_namespace/components/welcome_spec.js spec/frontend/vue_shared/new_namespace/new_namespace_page_spec.js spec/frontend/work_items/components/design_management/design_item_spec.js

1 remaining failing spec expected!