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- It's simpler to read for international audience.
- Past and future are more ambiguous regarding to when the thing
  happened or will happen.
- People troubleshooting or following procedures are living in the
  present tense, step by step.

See #16221

We have many old strings that don't match this guideline but we try to
update them whenever we modify or move a string, because any minor
change alreay breaks existing translations.

We're already capitalizing Boot Menu, Secure Boot, and Troubleshooting
Mode.

They are unique right now on this page so it's not a problem, but they
are also common terms that might want to use again on the same page at
some point.

Merge branch 'master' of https://gitlab.tails.boum.org/tails/tails into doc/17862-remove-email-Help-Desk-instructions