Fix promoCode Regex to include valid suffix

[btlechowski]

Fix #13089

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed. (Ask a Brave employee to help if you cannot access this document.)

Test Plan:

1. Open Firefox
2. Download Brave from https://staging.brave.com/ABC-123
3. Download again Brave from https://staging.brave.com/ABC-123
4. Run downloaded file from 3.

Expected Result:
promoCode file is created inside user-data dir with the contents: ABC123

Repeat for Chrome and Safari

Reviewer Checklist:

• Request a security/privacy review as needed if one was not already requested.

Tests
https://regex101.com/r/1ymYY3/3/
https://regex101.com/r/ehl7rC/1

• Adequate test coverage exists to prevent regressions
• Tests should be independent and work correctly when run individually or as a suite ref
• New files have MPL2 license header

[codecov-io]

Codecov Report

Merging #13091 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #13091   +/-   ##
=======================================
  Coverage   56.31%   56.31%           
=======================================
  Files         280      280           
  Lines       27581    27581           
  Branches     4497     4497           
=======================================
  Hits        15533    15533           
  Misses      12048    12048

Flag	Coverage Δ
#unittest	56.31% <100%> (ø)	⬆️

Impacted Files	Coverage Δ
app/cmdLine.js	39.8% <100%> (ø)	⬆️

[bsclifton]

++

[bsclifton]

master f8f0eb7
0.22.x 6cd3cca
0.21.x fdea0f3
0.20.x 46b84c7

[petemill]

Unfortunately the bash regex is not valid. Reported with #13112 and fix is incoming - but thanks for the Windows contribution!