[Documentation]: GCC toolset is now 13 but documented as 12

[stellaraccident]

Description of errors

As of #1745 the gcc toolset is 13. This doc still lists it as 12: https://github.com/ROCm/TheRock/blob/main/docs/environment_setup_guide.md

Attach any links, screenshots, or additional evidence you think will be helpful.

No response

[jayhawk-commits]

Documentation update will be included in #1746 when the workflows are updated to use the new docker.

[jayhawk-commits]

#1746 has been merged