Update anishathalye/proof-html action to v2

Author: renovate[bot]

.github/workflows/proof-html.yml

@@ -8,6 +8,6 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: anishathalye/proof-html@v1.4.2
+      - uses: anishathalye/proof-html@v2.2.1
         with:
           directory: ./