Philip: Hmm, so I went looking to see what I have on my machine. (here's the pedantic results;-)
1. I started by typing "toast" into the taskbar search box. Got no sensible results.
2. Tried typing "wintoast" and the search box found (best match) "Git for Windows" (App) [with those capitals]
3. right clicked on the icon and selected 'Open File Location`, which started an explorer window at:
> This PC > Win10 OS SSD (C:) > Users > Phili > AppData > Roaming > Microsoft > Windows > Start Menu > Programs
Highlighted was the "Git for Windows" shortcut file dated 07/10/2018 2KB
4. Right click shortcut file and select Properties. Target and Start in are set to "C:\Program Files\Git\mingw64\bin\wintoast.exe"
So given that I'm uptodate with the recent security fixes (used same setting box ticked -> git version 2.26.2.windows.1), and browerowy's comments about removal/replaced, it does look as if it is installed from somewhere in the Git install, and is left untouched if there is no change to the app.
Philip