Externalize admin settings strings

What does this MR do?

These MRs externalize some of the admin area strings.

This MR is leftover externalizations that weren't worth splitting.

Table of MRs

scope	CE MR	EE MR
leftover	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24708 (this MR)	TBD
instance statistics	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24709	TBD
jobs	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24710	TBD
services	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24711	TBD
deploy keys	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24712	TBD
hooks	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24713	TBD
applications	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24714	TBD
broadcast	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24715	TBD
abuse reports	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24716	TBD
appearances	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24717	TBD
runners	https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24718	TBD

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer