Remove repeat to expand decomposition

[ddilbazTT]

Ticket

None

Problem description

With stablehlo fusing merged in, there is no need for repeat to expand decomposition.
tenstorrent/tt-mlir@905f19e
Removing repeat -> expand decomposition as it is redundant.

Checklist

• GPT-OSS-20B passing: https://github.com/tenstorrent/tt-xla/actions/runs/21952180736

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 28.33%. Comparing base (77255e9) to head (a6c5c6b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3287   +/-   ##
=======================================
  Coverage   28.33%   28.33%           
=======================================
  Files          33       33           
  Lines        4094     4094           
=======================================
  Hits         1160     1160           
  Misses       2934     2934           

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