fix(java): correct SimpleJavaFileObject override - getCharContent not getContent

Co-authored-by: edburns <75821+edburns@users.noreply.github.com>

Author: Copilot

java/src/test/java/com/github/copilot/tool/SchemaGeneratorTest.java

@@ -55,7 +55,7 @@ private static class InMemorySource extends SimpleJavaFileObject {
         }
 
         @Override
-        public CharSequence getContent() throws IOException {
+        public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
             return code;
         }
     }