MM-26015: ensure admin retains permissions to team after being removed from a team (#14961)

Summary:
Ensure admin retains permissions to team after being removed from a team

Ticket Link:
https://mattermost.atlassian.net/browse/MM-26015

app/authorization_test.go

@@ -52,4 +52,10 @@ func TestHasPermissionToTeam(t *testing.T) {
 	th.RemoveUserFromTeam(th.BasicUser, th.BasicTeam)
 
 	assert.False(t, th.App.HasPermissionToTeam(th.BasicUser.Id, th.BasicTeam.Id, model.PERMISSION_LIST_TEAM_CHANNELS))
+
+	th.LinkUserToTeam(th.SystemAdminUser, th.BasicTeam)
+	assert.True(t, th.App.HasPermissionToTeam(th.SystemAdminUser.Id, th.BasicTeam.Id, model.PERMISSION_LIST_TEAM_CHANNELS))
+	th.RemoveUserFromTeam(th.SystemAdminUser, th.BasicTeam)
+	// This used to fail before MM-26015
+	assert.True(t, th.App.HasPermissionToTeam(th.SystemAdminUser.Id, th.BasicTeam.Id, model.PERMISSION_LIST_TEAM_CHANNELS))
 }