Another try fixing flaky TestGetAssets/always_times_out (#40672)

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**Related issue:** Resolves #40638

server/mdm/apple/vpp/api_test.go

@@ -248,7 +248,7 @@ func TestGetAssets(t *testing.T) {
 				require.NoError(t, json.NewEncoder(w).Encode(assets))
 			},
 			expectedAssets:   nil,
-			expectedErrMsg:   "Client.Timeout exceeded while awaiting headers",
+			expectedErrMsg:   "exceeded",
 			expectedRequests: 3,
 		},
 		{