Rename unused arguments to start with underscore

[telotortium]

Otherwise, the byte compiler complains with errors like this:

In toplevel form:
third_party/elisp/request/tests/test-request.el:188:1:Error: Unused lexical argument `args'

You can tell the byte compiler the variable is unused by giving it a name starting with an underscore (_) (manual).

[dickmao]

Thanks.