chore: enable trustPolicyExcludePrune (#14695)

Explain what changed and why. Reference issues here too (Closes pnpm/pnpm#123).

pnpm-workspace.yaml

@@ -542,12 +542,12 @@ trustPolicy: no-downgrade
 trustPolicyExclude:
   - '@pnpm/*'
   - '@yarnpkg/libzip@3.2.2'
-  - fastq@1.20.2
   - pnpm
   - rxjs@7.8.2
-  - tinyexec@1.2.2
   - undici-types@6.21.0
 
+trustPolicyExcludePrune: true
+
 trustPolicyIgnoreAfter: 10080 # 1 week
 
 # Dependencies deliberately held back, which `pnpm update --latest` (run by the