Bump the actions group across 1 directory with 2 updates

Bumps the actions group with 2 updates in the / directory: [step-security/harden-runner](https://github.com/step-security/harden-runner) and [chainguard-dev/actions](https://github.com/chainguard-dev/actions).


Updates `step-security/harden-runner` from 2.14.2 to 2.15.0
- [Release notes](https://github.com/step-security/harden-runner/releases)
- [Commits](step-security/harden-runner@5ef0c07...a90bcbc)

Updates `chainguard-dev/actions` from 1.6.3 to 1.6.4
- [Release notes](https://github.com/chainguard-dev/actions/releases)
- [Commits](chainguard-dev/actions@4ed96e9...eab208e)

---
updated-dependencies:
- dependency-name: step-security/harden-runner
  dependency-version: 2.15.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: actions
- dependency-name: chainguard-dev/actions
  dependency-version: 1.6.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: actions
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/update-ca-cert.yaml

@@ -32,7 +32,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       - 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
       - name: Generate token for PR
@@ -121,7 +121,7 @@ jobs:
           fi
       - name: Setup gitsign
         if: steps.update.outputs.changed == 'true'
-        uses: chainguard-dev/actions/setup-gitsign@4ed96e952ef2982fe89a50f3c40e9643bb9fe803 # v1.6.3
+        uses: chainguard-dev/actions/setup-gitsign@eab208ef2d05b13404296a5e194a6b237e8bb213 # v1.6.4
       - name: Create Pull Request
         if: steps.update.outputs.changed == 'true'
         uses: peter-evans/create-pull-request@c0f553fe549906ede9cf27b5156039d195d2ece0 # v8.1.0