Update readme to reflect python versions in tox (#1076)

README.md

@@ -39,7 +39,7 @@ environments. First, install conda with tox and tox-conda in a base environment
 (eg. ``conda install -c conda-forge tox tox-conda``). Calls to ``tox`` can then be
 used to configure a development environment and run tests.
 
-First, setup a development conda environment via ``tox -e {env}`` where ``env`` is one of ``{py36,py37,py38,py39}``.
+First, setup a development conda environment via ``tox -e {env}`` where ``env`` is one of ``{py38,py39,py310}``.
 This will install fsspec dependencies, test & dev tools, and install fsspec in develop
 mode. You may activate the dev environment under ``.tox/{env}`` via ``conda activate .tox/{env}``.