Relax TestAdminCronTasks (#591)

Relax test since this will be variable upstream ...

Reviewed-on: https://gitea.com/gitea/go-sdk/pulls/591
Reviewed-by: Gusted <williamzijl7@hotmail.com>

gitea/admin_test.go

@@ -45,7 +45,7 @@ func TestAdminCronTasks(t *testing.T) {
 
 	tasks, _, err := c.ListCronTasks(ListCronTaskOptions{})
 	assert.NoError(t, err)
-	assert.Len(t, tasks, 21)
+	assert.True(t, len(tasks) > 15)
 	_, err = c.RunCronTasks(tasks[0].Name)
 	assert.NoError(t, err)
 }