Add inline TODO comment

tests/base-notebook/test_packages.py

@@ -66,6 +66,10 @@ EXCLUDED_PACKAGES = [
     "ca-certificates",
     "conda-forge::blas[build=openblas]",
     "hdf5",
+    # TODO(asalikhov)
+    # When we remove a workaround for arm regarding mamba, we can
+    # test installation of mamba as well and remove this exception.
+    # See: <https://github.com/jupyter/docker-stacks/issues/1539>
     "mamba[version='<0.18']",
     "openssl",
     "protobuf",