fix: assert UpdateGroup HTTP status in disabled group tests

Add require.Equal checks for 200 status after UpdateGroup calls
so the test fails immediately on API errors rather than relying
on the subsequent Eventually timeout.

test/s3/iam/s3_iam_group_test.go

@@ -520,6 +520,7 @@ func TestIAMGroupDisabledPolicyEnforcement(t *testing.T) {
 		})
 		require.NoError(t, err)
 		defer resp.Body.Close()
+		require.Equal(t, http.StatusOK, resp.StatusCode, "UpdateGroup (disable) should return 200")
 
 		// Wait for propagation — user should be denied
 		require.Eventually(t, func() bool {
@@ -538,6 +539,7 @@ func TestIAMGroupDisabledPolicyEnforcement(t *testing.T) {
 		})
 		require.NoError(t, err)
 		defer resp.Body.Close()
+		require.Equal(t, http.StatusOK, resp.StatusCode, "UpdateGroup (re-enable) should return 200")
 
 		// Wait for propagation — user should have access again
 		require.Eventually(t, func() bool {