🐛 (go/v4): Fix linter issues in the scaffold

[camilamacedo86]

This PR fix the following issues:

$ make lint
testdata/project-v4/bin/golangci-lint run
cmd/main.go:154:37: string  has 3 occurrences, make it a constant (goconst)
if os.Getenv(ENABLE_WEBHOOKS) != false {
                                   ^
api/v1/firstmate_webhook.go:25:5: var  is unused (unused)
var firstmatelog = logf.Log.WithName(firstmate-resource)

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: camilamacedo86

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [camilamacedo86]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[camilamacedo86]

I am moving forward because it is a nit/fix
We have big fishes to fry and we need help with a lot of PRs reviews.
So, I will not make nobody waste time on this one.