Pin nx to 20.8.3

Author: renovate[bot]

package.json

@@ -137,7 +137,7 @@
     "globby": "^16.0.0",
     "lerna": "^9.0.3",
     "markdownlint-cli2": "^0.18.1",
-    "nx": "^20.8.3",
+    "nx": "20.8.3",
     "playwright": "1.57.0",
     "prettier": "^3.6.2",
     "pretty-quick": "^4.2.2",