Bump fsspec from 2021.5.0 to 2021.6.0 (#782)

* Bump fsspec from 2021.5.0 to 2021.6.0

Bumps [fsspec](https://github.com/intake/filesystem_spec) from 2021.5.0 to 2021.6.0.
- [Release notes](https://github.com/intake/filesystem_spec/releases)
- [Commits](fsspec/filesystem_spec@2021.05.0...2021.06.0)

---
updated-dependencies:
- dependency-name: fsspec
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

* Bump s3fs at the same time

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Josh Moore <[email protected]>

Author: dependabot[bot]

requirements_dev_optional.txt

@@ -17,6 +17,6 @@ flake8==3.9.2
 pytest-cov==2.12.1
 pytest-doctestplus==0.4.0
 h5py==3.2.1
-s3fs==2021.5.0
-fsspec==2021.5.0
+s3fs==2021.6.0
+fsspec==2021.6.0
 moto[server]>=1.3.14