refactor: hide test-only encrypted key set reset

Keep clearEncryptedPropertyKeys() package-private so it is not part of the public API.

Co-authored-by: Cursor <cursoragent@cursor.com>

spring-cloud-starter-tencent-polaris-config/src/main/java/com/tencent/cloud/polaris/config/adapter/PolarisConfigPropertyAutoRefresher.java

@@ -495,7 +495,7 @@ public abstract class PolarisConfigPropertyAutoRefresher implements ApplicationL
 	 * Just for junit test. {@code encryptedPropertyKeys} is static and grow-only, so it has to be
 	 * reset between test methods.
 	 */
-	public static void clearEncryptedPropertyKeys() {
+	static void clearEncryptedPropertyKeys() {
 		encryptedPropertyKeys.clear();
 	}
 }