Fix grammar in bug report template

[sumaiazaman]

Description

This PR fixes a minor grammar issue in the bug report template.

Changes

• Changed "improper DocBlock" to "an improper DocBlock" in .github/ISSUE_TEMPLATE/Bug_report.yml for proper English grammar

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Testing

No testing required for this documentation fix.

Checklist

• I have read the contribution guidelines
• My code follows the code style of this project
• This change requires no documentation update
• I have made corresponding changes to the documentation (N/A)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works (N/A)
• New and existing unit tests pass locally with my changes (N/A)

[rodrigopedra]

If you notice an improper DocBlock, PHPStan, or IDE warnings while using Laravel...

DocBlock, PHPStan, or IDE are listed as types of improper warnings.

Expanding it would be like:

"If you notice improper DocBlock warnings, improper PHPStan warnings, or improper IDE warnings while using Laravel..."

I am not an English grammar expert, but it seems the added "an" article is unneeded in this case.