Various minor polishings

fix: Remove redundant null checks in ValidatePdoParameterBindingsRule

Fixed PHPStan errors by removing explicit null checks before instanceof.
The instanceof check handles both null and non-ArrayItem cases, making
the null comparison redundant and avoiding PHPStan's "always false" warning.

This resolves the PHPStan errors about strict comparison with null always
evaluating to false.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>