Fix/lint issues

[rafaelsousa]

### Description:

Fixes #(issue)

Checklist:

• [x] Tests included.
• [x] Lint and formatter run with no errors.
• [x] Tests all pass.

Where applicable:

• [ ] Public APIs match existing style.
• [ ] Any breaking changes have a deprecation path or have been discussed.
• [ ] Updated the vendor folder (using go mod vendor).

[coveralls]

Pull Request Test Coverage Report for Build 3918897145

• 0 of 78 (0.0%) changed or added relevant lines in 7 files are covered.
• 29 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.4%) to 29.311%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
modules/status/brightness.go	0	2	0.0%
internal/ui/about.go	0	4	0.0%
internal/ui/settings_ui.go	0	4	0.0%
internal/x11/wm/stack.go	0	4	0.0%
internal/x11/property.go	0	8	0.0%
internal/x11/wm/property.go	0	12	0.0%
internal/x11/wm/desk.go	0	44	0.0%
<!--	Total:	0	78	0.0%	-->

Files with Coverage Reduction	New Missed Lines	%
internal/x11/wm/desk.go	1	1.23%
modules/status/brightness.go	1	0%
internal/ui/launcher.go	8	50.36%
internal/ui/widgetpanel.go	19	70.18%
<!--	Total:	29		-->

Totals
Change from base Build 3878300944:	-0.4%
Covered Lines:	1535
Relevant Lines:	5237

---

💛 - Coveralls

[Jacalz]

It looks like there still are a few places where ioutil has been removed. That will need to be added back.

[rafaelsousa]

We can't use os.ReadFile yet as we support back to Go 1.14 and it was not present then.

The os.Readfile references were reverted.