Read Signature.bundled instead of suppressing UnusedVariable

The 21.X.X merge brought in Signature, whose bundled field only went
into the serialized signature and carried a suppression. jars() now
picks the jars by it: the hash is there exactly when the build declared
none of its own, so the step formats with the same jars as before.

Author: abashev

gradle-open-java-format/src/main/java/com/palantir/javaformat/gradle/spotless/PalantirJavaFormatStep.java

@@ -84,8 +84,7 @@ Signature sign() throws IOException {
     static final class Signature implements Serializable {
         private static final long serialVersionUID = 1L;
 
-        // Spotless compares the signature in its serialized form, and reads nothing out of it.
-        @SuppressWarnings("UnusedVariable")
+        /** The hash of the plugin's own jars, or empty when the build declared its own. */
         private final String bundled;
 
         private final FileSignature override;
@@ -100,7 +99,7 @@ static final class Signature implements Serializable {
         }
 
         List<File> jars() {
-            return BundledFormatter.jarsUnlessOverridden(override.files(), gradleUserHome);
+            return bundled.isEmpty() ? List.copyOf(override.files()) : BundledFormatter.jars(gradleUserHome);
         }
     }