chore: remove duplicate package.json file

The additional package.json file, which was copied to
build/cjs/package.json, did hide the parent one, leading to several
issues and providing no real feature. The other one, copied to
build/esm/package.json, is needed though, to enforce the module type.

Related:

- socketio/socket.io#4194
- #1513

Author: darrachequesne

postcompile.sh

@@ -1,6 +1,5 @@
 #!/bin/bash
 
-cp ./support/package.cjs.json ./build/cjs/package.json
 cp ./support/package.esm.json ./build/esm/package.json
 
 cp -r ./build/esm/ ./build/esm-debug/