Remove 'latest' jobs from Travis CI to build aarch64 wheels

[hugovk]

So we can build aarch64 wheels for 8.1.0.

I suggest we get everything in place, then:

1. Go to https://travis-ci.com/github/python-pillow/pillow-wheels
2. More options -> Trigger build
3. Cross our fingers and hope we get wheels we can then upload to PyPI

If they all start at the same time, they'll be allowed to finish, as negative balances are allowed. But no new builds once negative.

https://travis-ci.com/organizations/python-pillow/plan says:

We also have this to determine the upload:

# Upload wheels to GitHub Releases
deploy:
  provider: releases
  api_key:
    secure: PTgVG7DrYa2FTSQOq0eDaHDZb1vy0vf6MulyuoXMg8rssPQgJ/mYxRpNDK4V0EKolpN7f8s/OGg+fpNNtp5pOCJGsx0Okcf+YB2ac+Xl7DQPBucbDKFXs1ndf/ny6umk0TXX8JTrDp/mJDJf401yx1+qsZ6X/PFvchXvXVrQ+SQ=
  file_glob: true
  file: "${TRAVIS_BUILD_DIR}/${WHEEL_SDIR}/*.whl"
  on:
    condition: -z "$LATEST"
    repo: python-pillow/pillow-wheels
    tags: true
  skip_cleanup: true

We've already made the tags, so will removing tags: true be enough?

[hugovk]

Let's give this a shot!

[radarhere]

So is the plan to revert this once the wheels are distributed, or just to leave it, since we need to move away from Travis anyway?

[hugovk]

We can leave it like this, as Travis is currently set not to trigger for pushes or PRs, and will only run when manually triggered.

For the next release, if we still haven't fully migrated away yet, we can either manually trigger a build when ready (like just now), or temporarily enable builds just before the tag is pushed (so the release files go under a tag) and then disable again right after.

[janaknat]

Will there be Pillow aarch64 wheels for the latest release?

[radarhere]

aarch64 wheels have now been uploaded to PyPI