Update updateCheck and addonStore URLs to use new NV Access endpoints (#17680)
Summary of the issue:
NV Access has changed the update check and add-on store endpoint URLS.
While these are forwarded for now, NVDA should migrate over
Description of user facing changes
Use new URLs
Description of development approach
Use new URLs
Testing strategy:
Tested by setting mirrors manually in NVDA settings
Known issues with pull request:
None