[MLGO] Drop outdated comment in mlgo-utils README

The mlgo-utils README contained a comment about a deviation in the
python version requirement for itself and the rest of the project. Now
that the global LLVM minimum python version is 3.8, this comment is no
longer valid so remove it.

Author: boomanaiden154

llvm/utils/mlgo-utils/README.md

@@ -4,9 +4,3 @@ This folder contains MLGO Python utilities, particularly infrastructure
 to help enable ML applications within LLVM, especially tooling to extract
 corpora that can be used in downstream projects to train ML models and perform
 other tasks that benefit from having a large amount of data.
-
-### Python Versioning
-
-Due to type annotations, the MLGO tooling currently only supports a Python
-version greater than 3.8, deviating from the current LLVM project-wide
-minimum supported version of Python 3.6.