Change Max Player Count error type to warning - ISXB-719

[Pauliusd01]

Description

Changed the error type to warning, I agreed with the user report that from our own descriptions (https://www.foundations.unity.com/patterns/errors-and-messaging#Message-Types) the warning type is more fitting. But feel free to disagree if there's a good reason this is an error, will close it

Changes made

Please write down a short description of what changes were made.

Notes

Please write down any additional notes, remove the section if not applicable.

Checklist

Before review:

• Changelog entry added.
  • Explains the change in Changed, Fixed, Added sections.
  • For API change contains an example snippet and/or migration example.
  • FogBugz ticket attached, example ([case %number%](https://issuetracker.unity3d.com/issues/...)).
  • FogBugz is marked as "Resolved" with next release version correctly set.
• Tests added/changed, if applicable.
  • Functional tests Area_CanDoX, Area_CanDoX_EvenIfYIsTheCase, Area_WhenIDoX_AndYHappens_ThisIsTheResult.
  • Performance tests.
  • Integration tests.
• Docs for new/changed API's.
  • Xmldoc cross references are set correctly.
  • Added explanation how the API works.
  • Usage code examples added.
  • The manual is updated, if needed.

During merge:

• Commit message for squash-merge is prefixed with one of the list:
  • NEW: ___.
  • FIX: ___.
  • DOCS: ___.
  • CHANGE: ___.
  • RELEASE: 1.1.0-preview.3.

[ekcoh]

LGTM, seems it needs to be updated from develop, then ok to merge