Bugfix: Mixed precision: scheduler and optimizer are called in the wr…

[javierlorenzod]

…ong order (#5558)

What does this PR do?

Fixes # (issue) <- this links related issue to this PR

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[codecov]

Codecov Report

Merging #5997 (d48c850) into master (6dba266) will decrease coverage by 44%.
The diff coverage is 26%.

@@           Coverage Diff            @@
##           master   #5997     +/-   ##
========================================
- Coverage      90%     46%    -44%     
========================================
  Files         170     160     -10     
  Lines       11784   11203    -581     
========================================
- Hits        10664    5205   -5459     
- Misses       1120    5998   +4878     

[pep8speaks]

Hello @javierlorenzod! Thanks for updating this PR.

• In the file pytorch_lightning/trainer/connectors/optimizer_connector.py:

Line 76:21: E113 unexpected indentation