Suppress AccessController deprecation warning

AccessController has been deprecated for removal since Java 17 as part of JEP 411.
Since snappy-java needs to maintain compatibility with Java 8+, we cannot remove
the AccessController.doPrivileged calls. This commit adds @SuppressWarnings("removal")
to suppress the deprecation warning while maintaining backward compatibility.

The AccessController calls are used to bypass SecurityManager restrictions when
cleaning DirectByteBuffers. In Java 17+, these calls effectively just run the
action directly since SecurityManager is being phased out.

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

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

Author: xerial

src/main/java/org/xerial/snappy/pool/DirectByteBuffers.java

@@ -20,6 +20,7 @@
 /**
  * Utility to facilitate disposing of direct byte buffer instances.
  */
+@SuppressWarnings("removal")  // AccessController is deprecated for removal in Java 17+
 final class DirectByteBuffers {
 
     /**