Fix version comment for actions/setup-go to match v6.4.0 SHA

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: monorkin

.github/workflows/release.yml

@@ -41,7 +41,7 @@ jobs:
           persist-credentials: false
 
       - name: Set up Go
-        uses: actions/setup-go@4a3601121dd01d1626a1e23e37211e3254c1c06c # v6.3.0 # zizmor: ignore[cache-poisoning] -- cache is branch-isolated; fork PRs cannot write to this cache
+        uses: actions/setup-go@4a3601121dd01d1626a1e23e37211e3254c1c06c # v6.4.0 # zizmor: ignore[cache-poisoning] -- cache is branch-isolated; fork PRs cannot write to this cache
         with:
           go-version-file: go.mod