Clean some unused leftover headers in pipelines.cpp

[paul0403]

Context:
#2259 removed the pipeline definition from mlir/lib/Driver/pipelines.cpp, to have a single source of truth pipeline registry 🥳

There are some left over dialect and pass headers that are no longer needed.

Description of the Change:
Delete unused headers.

Benefits:
Cleaner code.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.07%. Comparing base (96b34bc) to head (798a01f).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2733   +/-   ##
=======================================
  Coverage   97.07%   97.07%           
=======================================
  Files         164      164           
  Lines       18703    18703           
  Branches     1766     1766           
=======================================
  Hits        18156    18156           
  Misses        397      397           
  Partials      150      150           

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[dime10]

Thanks!