No Bug: Remove swiftlint step from gh actions

[iccub]

Swiftlint is now preinstalled on macOS instances.
https://github.com/actions/virtual-environments/blob/main/images/macos/macos-10.15-Readme.md#linters

Without this change I see following error in logs, it started to happen today

The formula built, but is not symlinked into /usr/local
Could not symlink bin/swiftlint
Target /usr/local/bin/swiftlint
already exists. You may want to remove it:
  rm '/usr/local/bin/swiftlint'

Summary of Changes

This pull request fixes #

Submitter Checklist:

• Unit Tests are updated to cover new or changed functionality
• User-facing strings use NSLocalizableString()

Test Plan:

Screenshots:

Reviewer Checklist:

• Issues include necessary QA labels:
  • QA/(Yes|No)
  • release-notes/(include|exclude)
  • bug / enhancement
• Necessary security reviews have taken place.
• Adequate unit test coverage exists to prevent regressions.
• Adequate test plan exists for QA to validate (if applicable).
• Issue is assigned to a milestone (should happen at merge time).