Always include --CONTEXT-- placeholder in all extracted messages

[rtibbles]

Summary

• Restores the addition of the --CONTEXT-- placeholder in all extracted strings.

References

Follow up from #8224

Reviewer guidance

Do strings with no context still have the --CONTEXT-- placeholder in them when uploaded to crowdin?

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[radinamatic]

--CONTEXT-- is back! 🎉

I checked out the PR branch and uploaded the strings to the test radina-context branch/folder on Crowdin:

radina-context	release-v0.15.x

[radinamatic]

LGTM, thank you for bringing this back!