Fix GH Action

[arthurpalves]

What does this PR do

• Fixes our GH action to switch variants, so that it automatically installs the right version using homebrew.
• If using a macos-12 runner, homebrew will install using a packaged bottle, taking seconds.
• Remove steps to prepare a ci build from a previously committed binary, reliant on a manual step

How can it be tested

0. Ensure your workflow is running on macos-12 and not macos-latest.

1. Given the following step, variants switch should succeed, installing the latest version (since 1.1.4 is higher and inexistent as of now):

    - uses: backbase/variants@fix/gh-action
      with:
        version: 1.1.4
        platform: ios
        variant: beta
        verbose: true

2. Given the following step, variants switch should succeed, installing the latest version (when omitted, 'version' defaults to 'latest'):

    - uses: backbase/variants@fix/gh-action
      with:
        platform: ios
        variant: beta
        verbose: true

3. Given the following step, variants switch should succeed, installing version 1.1.1:

    - uses: backbase/variants@fix/gh-action
      with:
        version: 1.1.1
        platform: ios
        variant: beta
        verbose: true

4. Given the following step, variants switch should fail. The version is expected in the format 'major.minor.patch' / 'x.y.z':

    - uses: backbase/variants@fix/gh-action
      with:
        version: 1.1
        platform: ios
        variant: beta
        verbose: true

Task

resolves #189

Checklist:

• I ran make validation locally with success
• I have not introduced new bugs
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new errors