Flaky test: TerminalConfigHelper - isMonospace sans-serif

[alexdima]

Failed on Windows in https://github.com/microsoft/vscode/runs/1787065378?check_suite_focus=true#step:13:7812

  6497 passing (2m)
  42 pending
  1 failing

  1) Workbench - TerminalConfigHelper
       TerminalConfigHelper - isMonospace sans-serif:
     Error: Timeout of 5000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.