fix test to expect new exception

Author: billwert

sdk/identity/azure-identity/src/test/java/com/azure/identity/ManagedIdentityCredentialTest.java

@@ -157,7 +157,7 @@ public void testCloudshellUserAssigned() {
         ManagedIdentityCredential credential
             = new ManagedIdentityCredentialBuilder().configuration(configuration).objectId(OBJECT_ID).build();
         StepVerifier.create(credential.getToken(request))
-            .expectErrorMatches(t -> t instanceof CredentialUnavailableException)
+            .expectErrorMatches(t -> t instanceof ClientAuthenticationException)
             .verify();
     }