[llvm] Revert "[bazel][mlir][python] Port #155741: stub auto-generation (#157173)" (PR #157995)

[Jordan Rupprecht via llvm-commits]

rupprecht wrote:

For us, the downstream pyi files seemed to not actually be needed. Do you see breakage if the pyi files are missing?

@jpienaar 

https://github.com/llvm/llvm-project/pull/157995