Bump autobahn from 20.7.1 to 20.12.3 in /jmclient

Bumps [autobahn](https://github.com/crossbario/autobahn-python) from 20.7.1 to 20.12.3.
- [Release notes](https://github.com/crossbario/autobahn-python/releases)
- [Changelog](https://github.com/crossbario/autobahn-python/blob/master/docs/changelog.rst)
- [Commits](https://github.com/crossbario/autobahn-python/compare/v20.7.1...v20.12.3)

---
updated-dependencies:
- dependency-name: autobahn
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

jmclient/setup.py

@@ -11,6 +11,6 @@ setup(name='joinmarketclient',
       packages=['jmclient'],
       install_requires=['joinmarketbase==0.9.2', 'mnemonic', 'argon2_cffi',
                         'bencoder.pyx>=2.0.0', 'pyaes', 'klein==20.6.0',
-                        'pyjwt==2.1.0', 'autobahn==20.7.1'],
+                        'pyjwt==2.1.0', 'autobahn==20.12.3'],
       python_requires='>=3.6',
       zip_safe=False)