Update pnpm to v8.15.6 (#551)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -15,9 +15,9 @@
   "devDependencies": {
     "release-plan": "^0.8.0"
   },
-  "packageManager": "pnpm@8.15.4",
+  "packageManager": "pnpm@8.15.6",
   "volta": {
     "node": "16.20.2",
-    "pnpm": "8.15.4"
+    "pnpm": "8.15.6"
   }
 }