Actually, even though I couldn't run the 2nd line of this below, when I reinstalled it, it still worked and my old org was finally removed. Note: I also had to delete the shortcut on my desktop after I uninstalled it.
rm -rf ~/Library/Group Containers/UBF8T346G9.com.microsoft.teams
rm -rf ~/Library/Containers/com.microsoft.teams2
Problem solved.