Update taiki-e/install-action digest to 5a81a31

Author: nextest-bot

.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
       - name: Lint (rustfmt)
         run: cargo xfmt --check
       - name: Install cargo readme
-        uses: taiki-e/install-action@e29814c376696105d80cec9e9efaa98bae8e7347 # v2
+        uses: taiki-e/install-action@5a81a310d23893f77fe1a6876943901e1c1290e2 # v2
         with:
           tool: cargo-readme
       - name: Run cargo readme