CI: update experimental to Agda commit f3697415

Author: andreasabel

.github/workflows/ci-ubuntu.yml

@@ -76,7 +76,7 @@ jobs:
           if [[ '${{ github.ref }}' == 'refs/heads/experimental' \
              || '${{ github.base_ref }}' == 'experimental' ]]; then
             # Pick Agda version for experimental
-            echo "AGDA_COMMIT=tags/v2.8.0" >> "${GITHUB_ENV}";
+            echo "AGDA_COMMIT=f3697415ac835c4e0898fb7eb0a5a46e313c2065" >> "${GITHUB_ENV}";
             echo "AGDA_HTML_DIR=html/experimental" >> "${GITHUB_ENV}"
           else
             # Pick Agda version for master