sql: don't start default test tenant in MT admin function tests

These tests themselves start multiple tenants, so there is no need to
create a default test tenant (doing that also makes it a bit more
confusing because the default tenant as well as the first test tenant
share the same TenantID effectively making it two SQL pod config, which
is confusing). Starting the default test tenant was enabled recently in
c899661 when we enabled the CCL
license, and we have seen at least one confusing failure that is
possibly related to this.

Starting the default test tenant was originally added in
cfa4375, but I don't see a good reason
for it.

Release note: None

Author: yuzefovich

pkg/sql/multitenant_admin_function_test.go

@@ -246,7 +246,7 @@ func (tc testCase) runTest(
 	if numNodes == 0 {
 		numNodes = 1
 	}
-	cfg.ServerArgs.DefaultTestTenant = base.TestTenantProbabilistic
+	cfg.ServerArgs.DefaultTestTenant = base.TestControlsTenantsExplicitly
 	testCluster := serverutils.StartNewTestCluster(t, numNodes, cfg.TestClusterArgs)
 	defer testCluster.Stopper().Stop(ctx)