Remove HTML in Import/Export related translations

What does this MR do?

Part of: #228846 (closed)

Remove direct usage of HTML in strings related to import so that these strings can be removed from the todolist and translated normally.

This is a follow up to https://gitlab.com/gitlab-org/gitlab/-/issues/217933 where we disallowed HTML in translations and moved all existing linter errors to a todolist.

Screenshots

Screen	Screenshot
GitHub Import
FogBugz User Map
Google Code Import
Issue Export
Repo Import

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done