Salam (Blessings) there!
I read the blog post in which Applevis community introduced the IOS 13.6. Also read the comments down there. A lot of users reporting there, whenever they want to delete the text from edit fields, in addition to deleting the text, voiceover also playing a 'boundary reach' sound. I myself experiencing this, and I agree, it is really annoying.
Workaround for this is:
goto: Settings > Accessibility > voiceover > audio > sounds
and select the boundary reach from there and turn off the sound for it.
Of course this also have some consequences that now vo wont tell you anywhere by sound that whether you're at the beginning or at the end of the page. You have to sacrifice one. :)
In the meantime I also request from you guys pl report this to accessibility guys at apple: