I got around this by using the Real Time Find and Replace plugin:

https://wordpress.org/support/plugin/real-time-find-and-replace

I added the find as target='_blank' and the replace as target='_blank' rel='noopener'

However, the reason I initially raised this issue wasn’t for a work around like mine or like the code change you have suggested. It was to point out that there is an issue with Enfold that needs to be fixed in a release of the the theme, not patched by the end users of your theme.

Thanks

Andy.