CI: fix CI to use rocqnavi release 0.3.1

Author: yoshihiro503

.github/workflows/generate_docs.yml

@@ -38,7 +38,7 @@ jobs:
         run: opam install -y --deps-only . && opam exec -- make -j 4
 
       - name: Install Rocqnavi
-        run: opam install -y rocq-navi.0.3.0
+        run: opam install -y rocq-navi.0.3.1
 
       - name: Generate Documents
         run: |