Add Mono download to linux test env

[eranturgeman]

• The pull request is targeting the dev branch.
• The code has been validated to compile successfully by running go vet ./....
• The code has been formatted properly using go fmt ./....
• All static analysis checks passed.
• All tests have passed. If this feature is not already covered by the tests, new tests have been added.
• Updated the Contributing page / ReadMe page / CI Workflow files if needed.
• All changes are detailed at the description. if not already covered at JFrog Documentation, new documentation have been added.

---

[github-actions]

Merging this branch will not change overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/jfrog/jfrog-cli-security/commands/audit	0.00% (ø)

---

Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/jfrog/jfrog-cli-security/commands/audit/scarunner.go	0.00% (ø)	0	0	0

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

[github-actions]

---

🐸 JFrog Frogbot