Remove references to mlir-hlo in docs

[joeycarter]

Catalyst no longer uses the mlir-hlo package, but we still reference it in a number of places in our docs, e.g.

https://github.com/PennyLaneAI/catalyst/blob/9376631b57b62d0153950142b8087baa807b6b9d/doc/dev/architecture.rst?plain=1#L154 https://github.com/PennyLaneAI/catalyst/blob/9376631b57b62d0153950142b8087baa807b6b9d/doc/dev/installation.rst#L242 https://github.com/PennyLaneAI/catalyst/blob/9376631b57b62d0153950142b8087baa807b6b9d/doc/dev/installation.rst#L295-L296 https://github.com/PennyLaneAI/catalyst/blob/9376631b57b62d0153950142b8087baa807b6b9d/doc/dev/installation.rst#L300-L301 https://github.com/PennyLaneAI/catalyst/blob/9376631b57b62d0153950142b8087baa807b6b9d/doc/dev/debugging.rst#L209-L210

The docs should be updated to reflect the recent migration from mlir-hlo to stablehlo (see #1921 for details).