Merge pull request #1758 from python-trio/dependabot/pip/isort-5.6.4

Author: dependabot-preview[bot]

test-requirements.txt

@@ -22,7 +22,7 @@ immutables==0.14          # via -r test-requirements.in
 iniconfig==1.0.1          # via pytest
 ipython-genutils==0.2.0   # via traitlets
 ipython==7.18.1           # via -r test-requirements.in
-isort==5.5.4              # via pylint
+isort==5.6.4              # via pylint
 jedi==0.17.2              # via -r test-requirements.in, ipython
 lazy-object-proxy==1.4.3  # via astroid
 mccabe==0.6.1             # via flake8, pylint