Fix up of: IA2: Do not treat huge base64 data as NVDA might freeze in Google Chrome (PR #10240) (#10282)
* Fix up of: IA2: Do not treat huge base64 data as NVDA might freeze in Google Chrome (PR #10240)
Ensure to truncate base64 data only in the `src` attribute, and not in an eventual
text content (eg. in and inline editor).
Re: https://github.com/nvaccess/nvda/pull/10231#issuecomment-535254306
* Fix up of bd35387cbe: Include the comma after "base64" in the capturing group