Make Use control test plan not mandatory
Make Use control test plan not mandatory

The field gets set to mandatory if it is set to not null on the model,
but test_plan_procedure has a default value that is used for all non set
fields so it explicit value can be omitted.

andrei-karalionak/ggrc-core,selahssea/ggrc-core,josthkko/ggrc-core,selahssea/ggrc-core,edofic/ggrc-core,josthkko/ggrc-core,plamut/ggrc-core,plamut/ggrc-core,josthkko/ggrc-core,VinnieJohns/ggrc-core,j0gurt/ggrc-core,kr41/ggrc-core,AleksNeStu/ggrc-core,AleksNeStu/ggrc-core,plamut/ggrc-core,VinnieJohns/ggrc-core,selahssea/ggrc-core,andrei-karalionak/ggrc-core,kr41/ggrc-core,edofic/ggrc-core,andrei-karalionak/ggrc-core,AleksNeStu/ggrc-core,kr41/ggrc-core,VinnieJohns/ggrc-core,kr41/ggrc-core,j0gurt/ggrc-core,AleksNeStu/ggrc-core,edofic/ggrc-core,andrei-karalionak/ggrc-core,j0gurt/ggrc-core,VinnieJohns/ggrc-core,j0gurt/ggrc-core,selahssea/ggrc-core,josthkko/ggrc-core,plamut/ggrc-core,edofic/ggrc-core