build: Expand lerna version range to accept v6 (#3417)

See #3409.

Even with the peerDependencies: optional, npm will *still* kick and scream and end your process if you try to use this with lerna v6.

Author: JaneJeon

@commitlint/config-lerna-scopes/package.json

@@ -27,7 +27,7 @@
   },
   "homepage": "https://commitlint.js.org/",
   "peerDependencies": {
-    "lerna": "^5.0.0"
+    "lerna": "^5.0.0 || ^6"
   },
   "peerDependenciesMeta": {
     "lerna": {