remove deprecated reload_dataloaders_every_epoch from Trainer

[rohitgr7]

What does this PR do?

Finishes and fixes #10312

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[tchaton]

LGTM !

[codecov]

Codecov Report

Merging #10481 (6f8f4ad) into master (6dfcb6a) will increase coverage by 0%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #10481   +/-   ##
=======================================
  Coverage      92%      92%           
=======================================
  Files         178      178           
  Lines       16243    16240    -3     
=======================================
  Hits        14904    14904           
+ Misses       1339     1336    -3     

[ananthsub]

doesn't this need to be an int?