package.json: drop 'prepare' script

'prepare' runs on every 'npm install' (no-args) in this repo, not just on
git-dep install — so it adds a build to the inner-loop. For testing pre-merge
conformance against an SDK, pkg.pr.new already publishes per-PR builds:

  npx https://pkg.pr.new/@modelcontextprotocol/conformance@<PR>

which doesn't need 'prepare'. 'prepack' covers npm publish.

Author: pcarleton

package.json

@@ -21,8 +21,7 @@
     "tier-check": "node dist/index.js tier-check",
     "check": "npm run typecheck && npm run lint",
     "typecheck": "tsgo --noEmit",
-    "prepack": "npm run build",
-    "prepare": "npm run build"
+    "prepack": "npm run build"
   },
   "files": [
     "dist"