Remove custom linter

[Samze]

Description of the Change

There appears to be have been a custom linter introduced a long time ago, this is currently failing when running make all with:

....
Running custom linters...
bash -c "go run bin/style/main.go api util"
api/shared/wrap_for_cf_on_k8s.go +99 type declaration certRoundTripper defined after a function declaration
api/shared/wrap_for_cf_on_k8s.go +104 method certRoundTripper.RoundTrip defined after function getCert
exit status 1
make: *** [custom-lint] Error 1

Instead of fixing the custom linter, lets just remove it and rely on golangci-lint

Why Is This PR Valuable?

Allows developers to do git clone && make on the repo.

How Urgent Is The Change?

Not urgent

[joaopapereira]

The change looks good.
The only non-blocking question is if we want to find a linter that checks if we use a function before we define it. I am ok with not adding that check.

[Samze]

The change looks good. The only non-blocking question is if we want to find a linter that checks if we use a function before we define it. I am ok with not adding that check.

Yeah, since unlike some interpreted languages golang has compile checks for functions and ordering doesn't matter, I'd personally be ok with not having this check.

[gururajsh]

LGTM