fix: align Kimi manifest with supported fields

.kimi-plugin/plugin.json

@@ -7,7 +7,6 @@
     "email": "jesse@fsck.com"
   },
   "homepage": "https://github.com/obra/superpowers",
-  "repository": "https://github.com/obra/superpowers",
   "license": "MIT",
   "keywords": [
     "brainstorming",