pyproject.toml: Update pytest-clarity and black

These seem to have much newer versions that didn't get updated in
this project due to the version pinning selector I was using with
poetry.

In the case of pytest-clarity the previous version was 0.3.1 and
the version selector was a caret (^), which will never update the
left-most (major) number. Now they seem to be on 1.x.x so it will
be OK in the future.

In the case of black, they use weird numbering so it's anyone's
guess how this will work! Luckily it's only used for linting and
formatting.

pyproject.toml

@@ -27,8 +27,8 @@ ftfy = "^5.9"
 pytest = "^6.1.1"
 ipython = { version = "^7.18.1", python = "^3.7" }
 flake8 = "^3.8.4"
-pytest-clarity = "^0.3.0-alpha.0"
-black = "20.8b1"
+pytest-clarity = "^1.0.1"
+black = "^21.6b0"
 isort = "^5.5.4"
 csvkit = "^1.0.5"