fix(test): Update TUF client test for public good signing config v0.2

Signed-off-by: Aaron Lew <[email protected]>

Author: aaronlew02

sigstore-java/src/test/java/dev/sigstore/tuf/SigstoreTufClientTest.java

@@ -49,16 +49,15 @@ public void testUpdate_publicGoodHasTrustedRootJson() throws Exception {
   }
 
   @Test
-  public void testUpdate_publicGoodNoSigningConfigV02() throws Exception {
+  public void testUpdate_publicGoodHasSigningConfigV02() throws Exception {
     var client =
         SigstoreTufClient.builder()
             .usePublicGoodInstance()
             .tufCacheLocation(localStorePath)
             .build();
     client.forceUpdate();
 
-    // TODO: change this when we publish new signing config to public good
-    Assertions.assertNull(client.getSigstoreSigningConfig());
+    assertSigningConfigValid(client.getSigstoreSigningConfig());
   }
 
   @Test