docs(metadata): drop stale "core module" reference in FileMetaDataLoaderTest

Post-WA4 the file-IO loader lives in the metadata module; refresh the
class javadoc to describe what the suite actually covers (loader
lifecycle, source registration, error paths) instead of the now-defunct
"core module coverage" framing.

Comment-only change. No behavioral impact.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: dmealing

server/java/metadata/src/test/java/com/metaobjects/loader/file/FileMetaDataLoaderTest.java

@@ -23,7 +23,8 @@
 import static org.junit.Assert.*;
 
 /**
- * Enhanced tests for FileMetaDataLoader to improve core module coverage
+ * Enhanced tests for FileMetaDataLoader covering loader lifecycle,
+ * source registration, and error paths.
  */
 public class FileMetaDataLoaderTest {