fix: freeze mypy

[Borda]

What does this PR do?

it seems that some newer version (recien=t update from 0.790 to 0.800) of mypy has a different interpretation of skip
the case is that the data/horovod files are in a folder without __init__ so they are not treated as a package so past setting does not have apply fully:

[mypy-tests.*]
ignore_errors = True

until there is resolution in python/mypy#8309 and python/mypy#4675, we freeze 0.790

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[codecov]

Codecov Report

Merging #5634 (8a8d3fd) into release/1.2-dev (f0fafa2) will increase coverage by 4%.
The diff coverage is n/a.

@@               Coverage Diff                @@
##           release/1.2-dev   #5634    +/-   ##
================================================
+ Coverage               89%     92%    +4%     
================================================
  Files                  153     153            
  Lines                10845   10845            
================================================
+ Hits                  9633   10022   +389     
+ Misses                1212     823   -389