try unfreeze torchtext

[Borda]

What does this PR do?

after update #6211 let's try unfreeze torchtext version
see: #3529 (comment)

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[codecov]

Codecov Report

Merging #6302 (0c415ff) into master (8001987) will decrease coverage by 0%.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #6302   +/-   ##
======================================
- Coverage      93%     93%   -0%     
======================================
  Files         160     160           
  Lines       11397   11397           
======================================
- Hits        10638   10609   -29     
- Misses        759     788   +29     

[Borda]

Docker failer is unrelated as it fails on miss-versions requested/downloaded 1.6 or nightly but always got 1.7.1 only
cc: @zcain117

#12 0.988 torch                     1.7.1
#12 0.988 torch-xla                 1.9+c865714

https://github.com/PyTorchLightning/pytorch-lightning/pull/6302/checks?check_run_id=2014014414#step:4:2272