Minor Fine-Tuning Scheduler Tutorial Updates for PTL 1.7

[speediedan]

Before submitting

• Did you make sure to update the docs?
• Did you write any new necessary tests?

What does this PR do?

A few minor updates to the Fine-Tuning Scheduler tutorial to better support the release of pytorch-lightning 1.7.x

• changed "finetuning" uses to "fine-tuning" since closed compound word version remains less common in the research literature for the time being
• removed use of CLI registry since it is deprecated in PTL 1.7 and simplifies the tutorial
• removed hydra-core version requirement since the relevant issue has been resolved
• added a small patch to address #80809 and allow the tutorial to succeed with torch 1.12.0. Despite the recent release of 1.12.1, the tutorial should work with 1.12.0 since a non-trivial number of users will likely continue to have it installed.

PR review

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

Did you have fun?

Make sure you had fun coding 🙃

[codecov]

Codecov Report

Merging #187 (0472d78) into main (58c88a9) will not change coverage.
The diff coverage is n/a.

@@         Coverage Diff         @@
##           main   #187   +/-   ##
===================================
  Coverage    75%    75%           
===================================
  Files         2      2           
  Lines       370    370           
===================================
  Hits        276    276           
  Misses       94     94           

[speediedan]

FYI, the validate Docs/ build-docs job is only failing due to a single stale pytorch-lightning link on the basic_gan nb

[tchaton]

Looks neat !