Update myst_parser to v0.17.2 (#8380)
Update myst_parser to v0.17.2 (#8380)

To resolve issue with the removed `attrs` module.

See: https://github.com/executablebooks/MyST-Parser/pull/557
rsalmaso/wagtail,zerolab/wagtail,rsalmaso/wagtail,wagtail/wagtail,zerolab/wagtail,thenewguy/wagtail,zerolab/wagtail,wagtail/wagtail,rsalmaso/wagtail,thenewguy/wagtail,wagtail/wagtail,zerolab/wagtail,wagtail/wagtail,rsalmaso/wagtail,wagtail/wagtail,thenewguy/wagtail,zerolab/wagtail,thenewguy/wagtail,rsalmaso/wagtail,thenewguy/wagtail