fix: remove metric-registry config

BREAKING CHANGE: the hard-coded "metrics-registry" config has been
removed.

This is not used by npm at all, and is also not used by any of the npm
modules that consume config.  npm does not send data to any metrics
server.

workspaces/config/lib/index.js

@@ -322,10 +322,6 @@ class Config {
 
     const { data } = this.data.get('default')
 
-    // the metrics-registry defaults to the current resolved value of
-    // the registry, unless overridden somewhere else.
-    settableGetter(data, 'metrics-registry', () => this.#get('registry'))
-
     // if the prefix is set on cli, env, or userconfig, then we need to
     // default the globalconfig file to that location, instead of the default
     // global prefix.  It's weird that `npm get globalconfig --prefix=/foo`