Update shells immediately if profile config is changed

[Tyriar]

Repro:

1. Create a new profile in settings.json
2. Open dropdown, it's out of date for up to 10 seconds.

[meganrogge]

fixed with

vscode/src/vs/workbench/contrib/terminal/browser/terminalService.ts

Line 340 in f934e05

private async _updateAvailableProfilesNow(): Promise<void> {