chore(deps): update dependency @oclif/plugin-help to v6

Author: renovate[bot]

package.json

@@ -16,7 +16,7 @@
   },
   "devDependencies": {
     "@oclif/dev-cli": "1.26.10",
-    "@oclif/plugin-help": "3.3.1",
+    "@oclif/plugin-help": "6.2.0",
     "@oclif/test": "1.2.9",
     "@salesforce/dev-config": "1.6.0",
     "@types/chai": "4.3.8",