Skip cattrs tests on 3.8 (#231)

Temporary workaround for the the failures in #230.
diff --git a/.github/workflows/third_party.yml b/.github/workflows/third_party.yml
index a25f5d6..fe1be65 100644
--- a/.github/workflows/third_party.yml
+++ b/.github/workflows/third_party.yml
@@ -298,7 +298,8 @@
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
+        # TODO: Add 3.8 back to this matrix (see #230)
+        python-version: ["3.7", "3.9", "3.10", "3.11"]
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps: