Removed the deprecated Trainer.data_parallel_device_ids function in favour of Trainer.device_ids

[krishnakalyan3]

What does this PR do?

Removes deprecated APIs.

resolves #12072

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[codecov]

Codecov Report

Merging #14422 (3108d6a) into master (1e04951) will increase coverage by 14%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #14422     +/-   ##
=========================================
+ Coverage      61%      76%    +14%     
=========================================
  Files         331      331             
  Lines       26650    26687     +37     
=========================================
+ Hits        16357    20233   +3876     
+ Misses      10293     6454   -3839     

[krishnakalyan3]

Thank you for the reviews @rohitgr7 and @awaelchli