Update step-security/harden-runner action to v2.15.0

Author: renovate[bot]

.github/workflows/jekyll-gh-pages.yml

@@ -30,7 +30,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@5ef0c079ce82195b2a36a210272d6b661572d83e # v2.14.2
+        uses: step-security/harden-runner@a90bcbc6539c36a85cdfeb73f7e2f433735f215b # v2.15.0
         with:
           egress-policy: audit
 
@@ -55,7 +55,7 @@ jobs:
     needs: build
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@5ef0c079ce82195b2a36a210272d6b661572d83e # v2.14.2
+        uses: step-security/harden-runner@a90bcbc6539c36a85cdfeb73f7e2f433735f215b # v2.15.0
         with:
           egress-policy: audit