chore(knip): drop the now-unused rg binary exemption

tool-fs-search no longer spawns rg from PATH after the packaged-binary
switch, so its per-workspace ignoreBinaries entry is stale.

knip.json

@@ -566,9 +566,6 @@
       "project": [
         "src/**/*.ts",
         "tests/**/*.ts"
-      ],
-      "ignoreBinaries": [
-        "rg"
       ]
     },
     "packages/mcp/mcp-client": {