chore(fastify): remove stray packageManager field from subpackage

packageManager belongs in the workspace root only (already at
pnpm@10.26.1). The stale pnpm@10.24.0 here causes corepack to attempt
a version switch when invoking pnpm from the package directory.
Also drop the pnpm engines entry to match sibling middleware packages.

Author: felixweinberger

packages/middleware/fastify/package.json

@@ -13,10 +13,8 @@
         "url": "git+https://github.com/modelcontextprotocol/typescript-sdk.git"
     },
     "engines": {
-        "node": ">=20",
-        "pnpm": ">=10.24.0"
+        "node": ">=20"
     },
-    "packageManager": "pnpm@10.24.0",
     "keywords": [
         "modelcontextprotocol",
         "mcp",