Resolves SonarQube S927 x2 in ExpressionVisitor.cs.
The interface parameter was named ``Equal`` on a ``VisitNotEquals`` method,
which is semantically wrong and forced implementations to mismatch.
Implementations already used ``notEqual``; rename the interface to match.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>