I've the same in Moodle 3.5.2 with Firefox.
in source of first.js (\lib\amd\src) :
* This is an empty module, that is required before all other modules.
* Because every module is returned from a request for any other module, this
* forces the loading of all modules with a single request.
I don't think you can 'remove' them. And what we see in the web browser is not what they've in the file.
It's related to the amd system, i suppose.
in amd or not and I've no trouble with these files.
What kind of errors do you have ?