Only matters if Microsoft sues. GitHub-owner era Microsoft tends to want to stay in the open source community’s good graces. (Plus I’m sure the owner would just change the name if MS asked, anyway)
That being said, this is also a diagramming tool… I probably would recommend changing it
They'd probably (or I hope they would) ask nicely first, cease-and-desist second, and sue as a last resort.
Whether or not Microsoft allows the use may not be fully at their discretion; or rather their earlier choices could tie their hands in regards to later choices if things go south.
This is a short read on the kinds of issues that start to crop up when you don't agressively enforce your trademarks:
https://trademarks.justia.com/742/75/visio-74275413.html