fix(mac_shortcut.sh): fix `shellcheck` errors

[myii]

PR progress checklist (to be filled in by reviewers)

• [ ] Changes to documentation are appropriate (or tick if not required)
• [ ] Changes to tests are appropriate (or tick if not required)
• [ ] Reviews completed

---

What type of PR is this?

Primary type

• [ ] [build] Changes related to the build system
• [ ] [chore] Changes to the build process or auxiliary tools and libraries such as documentation generation
• [ ] [ci] Changes to the continuous integration configuration
• [ ] [feat] A new feature
• [x] [fix] A bug fix
• [ ] [perf] A code change that improves performance
• [ ] [refactor] A code change that neither fixes a bug nor adds a feature
• [ ] [revert] A change used to revert a previous commit
• [ ] [style] Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc.)

Secondary type

• [ ] [docs] Documentation changes
• [ ] [test] Adding missing or correcting existing tests

Does this PR introduce a BREAKING CHANGE?

No.

Related issues and/or pull requests

Needs to be merged ASAP, so that the builds no longer fail, e.g. #232.

Describe the changes you're proposing

Fix these errors:

In mysql/files/mac_shortcut.sh line 5:
if [[ -e "{{ home }}/{{ user }}/Desktop/{{ app }}" ]] && [[ "${1}" -eq "remove" ]]
                                                                       ^------^ SC2154: remove is referenced but not assigned.
In mysql/files/mac_shortcut.sh line 8:
elif [[ -e "{{ dir }}/{{ app ~ '.app' if suffix else app }}" ]] && [[ "${1}" -eq "add" ]]
                                                                                 ^---^ SC2154: add is referenced but not assigned.

CC: @noelmcloughlin.

Pillar / config required to test the proposed changes

N/A.

Debug log showing how the proposed changes work

Travis lint job passes.

Documentation checklist

• [ ] Updated the README (e.g. Available states).
• [ ] Updated pillar.example.

Testing checklist

• [ ] Included in Kitchen (i.e. under state_top).
• [ ] Covered by new/existing tests (e.g. InSpec, Serverspec, etc.).
• [ ] Updated the relevant test pillar.

Additional context

[myii]

Thanks for the review, @aboe76. Merging quickly because builds are failing, needed before merging #232, for example.

[saltstack-formulas-travis]

:tada: This PR is included in version 0.52.3 :tada:

The release is available on GitHub release

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