Update documentation concerning return license instructions in activation page

As discussed [in here on Discord](https://discord.com/channels/710946343828455455/1175793166645997698/1229444176681111572), Unity Hub 3.7.0 doesn't have the option to return license anymore for Personal licenses.


Step 7 in here might need an update :

Documentation:
https://game.ci/docs/github/activation/#personal-license

Source (step 7):
https://github.com/game-ci/documentation/blob/main/docs/03-github/02-activation.mdx?plain=1#L51-L53

I do confirm that the Professional license still have the Return license button:


We might suggest to return the license for Professional license activation prior to trying it in the cloud here in the docs:

https://github.com/game-ci/documentation/blob/main/docs/03-github/02-activation.mdx?plain=1#L63-L67

👍

Open docs/03-github/02-activation.mdx and review the Personal license instructions around step 7, then compare the Professional license guidance around the referenced lines. Update the activation instructions to reflect the current Unity Hub behavior and clarify when returning a Professional license is applicable; verify both sections remain consistent.

Written by the indexing model from the issue text.