remove redundant accumulation normalization in manual optimization

[awaelchli]

What does this PR do?

This is a small code improvement. Passing normalize=trainer.accumulate_grad_batches is redundant as its value is always 1. In fact, a user setting a value greater than 1 is leading to an error message from the Trainer anyway, as this is an unsupported feature for manual optimization.

Before submitting

• Was this discussed/approved via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or internal minor changes/refactorings)

changelog update not required. The ManualOptimization loop changes are not not released.

PR review

Anyone in the community is free to review the PR once the tests have passed.
Before you start reviewing make sure you have read Review guidelines. In short, see the following bullet-list:

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified

Did you have fun?

I made sure I had fun coding 🙃

[github-actions]

Build Error! No Linked Issue found. Please link an issue or mention it in the body using #<issue_id>

[codecov]

Codecov Report

Merging #9769 (c25205b) into master (66ce443) will increase coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #9769   +/-   ##
======================================
  Coverage      93%     93%           
======================================
  Files         178     178           
  Lines       15650   15716   +66     
======================================
+ Hits        14492   14559   +67     
+ Misses       1158    1157    -1     

[github-actions]

Build Error! No Linked Issue found. Please link an issue or mention it in the body using #<issue_id>