[MC-106678] You can't leave only from one team

To reproduce, do these commands:

/scoreboard teams add testTeam1
/scoreboard teams add testTeam2
/scoreboard teams join testTeam1
/scoreboard teams join testTeam2
/scoreboard teams leave testTeam1 @p
/scoreboard teams list

Expected: No players in testTeam1 and 1 player in testTeam2
But instead there are no people in any of these teams