Remove SourceClear scan workflow due to security vulnerability

Removes the SourceClear workflow that contains a dangerous curl|bash pattern,
which presents risks of script injection and untrusted remote code execution
in the CI/CD pipeline. This follows the same remediation approach used in the
PHP SDK (optimizely/php-sdk#294).

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: Tamara-Barum