pnpm: remove update notifier message (#51630)

Having a bit fat dialog printed everytime I run pnpm install is a bit
annoying. I believe we manage the version used, so we don't actually
want to be using the latest on NPM. IE this dialog was misleading.

Test Plan: pnpm install didn't show the upgrade dialog.

Author: keegancsmith

.npmrc

@@ -16,3 +16,6 @@ public-hoist-pattern[]=global
 public-hoist-pattern[]=*eslint*
 
 auto-install-peers=true
+
+# We manage the version of pnpm so the update warnings based on NPM is inaccurate.
+update-notifier=false