pip prod(deps): update distributed requirement from <2021.4 to <2021.5
pip prod(deps): update distributed requirement from <2021.4 to <2021.5

Updates the requirements on [distributed](https://github.com/dask/distributed) to permit the latest version.
- [Release notes](https://github.com/dask/distributed/releases)
- [Changelog](https://github.com/dask/distributed/blob/main/docs/release-procedure.md)
- [Commits](https://github.com/dask/distributed/compare/1.1.0...2021.04.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
opesci/devito,opesci/devito