docs: republish waiting period (#20920)

Explicitly state that republishing an unpublished package requires a 72h waiting period.

PR-URL: npm/npm#20920
Credit: @gmattie
Reviewed-By: @zkat

doc/cli/npm-unpublish.md

@@ -28,9 +28,10 @@ version combination can never be reused.  In order to publish the
 package again, a new version number must be used.
 
 With the default registry (`registry.npmjs.org`), unpublish is
-only allowed with versions published in the last 24 hours. If you
-are trying to unpublish a version published longer ago than that,
-contact support@npmjs.com.
+only allowed with versions published in the last 72 hours.  Similarly,
+new versions of unpublished packages may not be republished until 72 hours
+have passed. If you are trying to unpublish a version published longer
+ago than that, contact support@npmjs.com.
 
 The scope is optional and follows the usual rules for `npm-scope(7)`.