Update pnpm to v9.12.0 (#5100)

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

api_tests/package.json

@@ -6,7 +6,7 @@
   "repository": "https://github.com/LemmyNet/lemmy",
   "author": "Dessalines",
   "license": "AGPL-3.0",
-  "packageManager": "pnpm@9.9.0",
+  "packageManager": "pnpm@9.12.0",
   "scripts": {
     "lint": "tsc --noEmit && eslint --report-unused-disable-directives && prettier --check 'src/**/*.ts'",
     "fix": "prettier --write src && eslint --fix src",