Update build/setuptools sdist CI checks

setuptools has been fixed to canonicalize the package name in sdist
names per the sdist spec (PEP 625). This requires that hyphens convert
to underscores.

Testing use of that sdist requires correct naming to match, naturally.

Author: sirosen

.github/workflows/build.yaml

@@ -51,11 +51,11 @@ jobs:
           python -m build --sdist
           version="$(grep '^version' setup.cfg |  cut -d '=' -f2 | tr -d ' ')"
           cd dist
-          tar -xzf "check-jsonschema-${version}.tar.gz"
+          tar -xzf "check_jsonschema-${version}.tar.gz"
       - name: test
         run: |
           version="$(grep '^version' setup.cfg |  cut -d '=' -f2 | tr -d ' ')"
-          cd "dist/check-jsonschema-${version}"
+          cd "dist/check_jsonschema-${version}"
           python -m tox run -m ci
 
   ci-test-matrix: