pin version of websockets

Fixes #

Changes proposed in this pull request:

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[ ] Change the base branch to dev if it is not already.
[ ] I've read and followed all steps in the Making a pull request section of the CONTRIBUTING docs.
[ ] I've updated or added any relevant docstrings following the syntax described in the Writing docstrings section of the CONTRIBUTING docs.
[ ] If this PR fixes a bug, I've added a test that will fail without my fix.
[ ] If this PR adds a new feature, I've added tests that sufficiently cover my new functionality.