Allow amp-autocomplete in email format by default

[caroqliu]

This PR removes the doc-level opt-in flag introduced in #27174, making amp-autocomplete fully valid and fully available in the AMP format by default. Closes #24881. This change is being implemented now as prompted by approval in a recent wg-amp4email meeting.

/cc @ampproject/wg-amp4email @nainar

[amp-owners-bot]

Hey @ampproject/wg-caching! These files were changed:

validator/testdata/amp4email_feature_tests/amp-autocomplete.html
validator/testdata/amp4email_feature_tests/amp-autocomplete.out
validator/validator-main.protoascii

[zhangsu]

I reviewed the recent changes to the working group meeting notes but found no mention of this. Was this only only approved verbally but not taken down in the notes?

I was under the impression that mail.ru and Yahoo! Mail still haven't implemented this feature yet, so this feature would only work in Gmail and the current warning would still make sense.

[caroqliu]

I reviewed the recent changes to the working group meeting notes but found no mention of this. Was this only only approved verbally but not taken down in the notes?

I was under the impression that mail.ru and Yahoo! Mail still haven't implemented this feature yet, so this feature would only work in Gmail and the current warning would still make sense.

I wasn't in attendance, but let's not do this if we don't have 100% confidence and documented consensus. @nainar will be the point person on bringing this up for the next agenda.

[caroqliu]

I reviewed the recent changes to the working group meeting notes but found no mention of this. Was this only only approved verbally but not taken down in the notes?
I was under the impression that mail.ru and Yahoo! Mail still haven't implemented this feature yet, so this feature would only work in Gmail and the current warning would still make sense.

I wasn't in attendance, but let's not do this if we don't have 100% confidence and documented consensus. @nainar will be the point person on bringing this up for the next agenda.

This appears to be approved in the July meeting for @ampproject/wg-amp4email, PTAL.

[caroqliu]

ping @ampproject/wg-caching for review please 🙏