Remove unused which dependency

Summary: This seems to be (no longer) in use.

Reviewed By: lblasa

Differential Revision: D50645270

fbshipit-source-id: 69cf276f97d960a16ffd3e48342420b33fa646da

desktop/flipper-server-core/package.json

@@ -44,7 +44,6 @@
     "serialize-error": "^8.1.0",
     "split2": "^4.1.0",
     "tmp": "^0.2.1",
-    "which": "^2.0.2",
     "ws": "^8.6.0",
     "xdg-basedir": "^4.0.0"
   },
@@ -63,7 +62,6 @@
     "@types/rsocket-tcp-server": "^0.0.2",
     "@types/split2": "^4.2.0",
     "@types/tmp": "^0.2.3",
-    "@types/which": "^2.0.1",
     "@types/ws": "^8.5.3",
     "mock-fs": "^5.2.0"
   },