Clarify semantic versioning approach

[RobPasMue]

As raised in the PyAnsys dev meeting, we should clarify that we are following Semantic versioning for our PyAnsys packages. We are also mentioning that we are following what other major players are doing... and they are not actually following SemVer. That statament should be removed.

Overall, we might want to rewrite that section for major clarification. See https://dev.docs.pyansys.com/how-to/releasing.html#semantic-versioning

[RobPasMue]

Pinging @ansys/pyansys-core