I18n for triggers

What does this MR do?

This MR:

• fixes the syntax for (non-)namespaced strings
• replaces double quotes with single quotes around strings which do not contain single quotes inside (much more common among files in /app/views/)

Almost all of the externalizations were introduced two months ago in !52284 (merged)

Screenshots

No visible changes to UI in English as expected

Before	After

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
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  • I have not included a changelog entry because _____.
• Code review guidelines
• Merge request performance guidelines
• Style 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

Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team