chore: fix homebrew publication

[dduportal]

This PR aims at fixing the homebrew tap publication (ref. https://github.com/updatecli/updatecli/runs/3801471145?check_suite_focus=true#step:10:138) during its initial creation with the v0.8.0 release.

The failure was due to the token GITHUB_TOKEN provided to goreleaser by github actions. This token is able to publish release or packages to the repository updatecli/updatecli, but it does not have any authorization for the repository that should host the homebrew's tap (updatecli/homebrew-updatecli).

This PR defines a second token in goreleaser configuration, only for the homebrew publication.
I've created a PAT for this, and tested it for an initial "manual" release for v0.8.0 and it worked:

brew tap updatecli/updatecli
==> Tapping updatecli/updatecli
Cloning into '/usr/local/Homebrew/Library/Taps/updatecli/homebrew-updatecli'...
remote: Enumerating objects: 4, done.
remote: Counting objects: 100% (4/4), done.
remote: Compressing objects: 100% (2/2), done.
remote: Total 4 (delta 0), reused 0 (delta 0), pack-reused 0
Receiving objects: 100% (4/4), done.
Tapped 1 formula (12 files, 6.7KB).
admin@MacBook-Pro-16-de-Dadou ~ % brew install updatecli      
==> Downloading https://github.com/dduportal/updatecli/releases/download/v0.8.0/updatecli_Darwin_x86_64.tar.gz
==> Downloading from https://github-releases.githubusercontent.com/333694256/eff55370-a4ae-41f1-973b-71fedd2d0334?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIWNJYAX4CSVEH53A%2F20211005%2Fus-east-1%2F
######################################################################## 100.0%
==> Installing updatecli from updatecli/updatecli
🍺  /usr/local/Cellar/updatecli/0.8.0: 5 files, 53.7MB, built in 6 seconds
admin@MacBook-Pro-16-de-Dadou ~ % updatecli version

VERSION

Application:	0.8.0
Golang     :	1.17.1 darwin/amd64
Build Time :	2021-10-05T10:29:07Z

admin@MacBook-Pro-16-de-Dadou ~ % which updatecli

But it uses the binaries published on my own fork of updatecli: a new release v0.8.1 is required after this PR (i'm taking care of it)