Update taiki-e/install-action digest to 939f4af

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@3e1dd227d968fb9fa43ff604bd9b0ccd1b714919 # v2
+        uses: taiki-e/install-action@939f4af9602e15ef93b3329722569cb907a004ff # v2
         with:
           tool: cargo-readme
       - name: Run cargo readme