Fix ImageryLayer doc typo

[jjspace]

Description

Small typo in the ImageryLayer docs showing a , instead of a ;

Issue number and link

Fixes #11698

Testing plan

• Build and load the docs locally
• Open the docs locally and check the code example is correct

Author checklist

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change
• I have added or updated unit tests to ensure consistent code coverage
• I have update the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

[jjhembd]

Thanks @jjspace !