Remove deprecated functions from accelerator.py

[four4fish]

What does this PR do?

function connect_precision_plugin and connect_training_type_plugin has been deprecated in v1.3, remove them in v1.5

Fixes #9018

Does your PR introduce any breaking changes? If yes, please list them.

Removes connect_precision_plugin and connect_training_type_plugin from the Accelerator API

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[codecov]

Codecov Report

Merging #9019 (0843eb4) into master (e1442d2) will decrease coverage by 4%.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #9019    +/-   ##
=======================================
- Coverage      93%     89%    -4%     
=======================================
  Files         175     175            
  Lines       14398   14395     -3     
=======================================
- Hits        13337   12756   -581     
- Misses       1061    1639   +578     

[ananthsub]

thanks for the cleanup! please add to the changelog too