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

[Jordan Rupprecht via llvm-commits]

rupprecht wrote:

Ok, wanted to make sure this was actually breaking things. Otherwise it seemed the original changes were a nice dead code cleanup :)

Sorry, I was out yesterday, otherwise I would have stamped sooner.

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