[FIX] membership: remove date_cancel for draft invoices
[FIX] membership: remove date_cancel for draft invoices

In `action_cancel` method below, the date_cancel is set when the linked invoice
is canceled.
When the canceled invoiced was reset to draft, the date_cancel was not removed.
This change makes sense as the state of the membership line is changed from
`cancel` to `waiting` when the invoice is reset to draft.

Closes #14313

vnsofthe/odoo,hip-odoo/odoo,vnsofthe/odoo,funkring/fdoo,storm-computers/odoo,vnsofthe/odoo,storm-computers/odoo,vnsofthe/odoo,hip-odoo/odoo,ehirt/odoo,alexcuellar/odoo,diagramsoftware/odoo,Adel-Magebinary/odoo,odootr/odoo,BT-ojossen/odoo,tvibliani/odoo,ehirt/odoo,Elico-Corp/odoo_OCB,spadae22/odoo,synconics/odoo,tvibliani/odoo,leorochael/odoo,bplancher/odoo,Adel-Magebinary/odoo,spadae22/odoo,dfang/odoo,Nowheresly/odoo,Elico-Corp/odoo_OCB,makinacorpus/odoo,Nowheresly/odoo,BT-ojossen/odoo,alexcuellar/odoo,leorochael/odoo,makinacorpus/odoo,Adel-Magebinary/odoo,ehirt/odoo,funkring/fdoo,datenbetrieb/odoo,makinacorpus/odoo,dfang/odoo,diagramsoftware/odoo,Nowheresly/odoo,alexcuellar/odoo,glovebx/odoo,BT-ojossen/odoo,glovebx/odoo,ehirt/odoo,BT-ojossen/odoo,bplancher/odoo,datenbetrieb/odoo,makinacorpus/odoo,Adel-Magebinary/odoo,funkring/fdoo,ygol/odoo,Daniel-CA/odoo,Elico-Corp/odoo_OCB,Adel-Magebinary/odoo,synconics/odoo,NeovaHealth/odoo,alexcuellar/odoo,tvibliani/odoo,diagramsoftware/odoo,Elico-Corp/odoo_OCB,glovebx/odoo,storm-computers/odoo,CatsAndDogsbvba/odoo,synconics/odoo,spadae22/odoo,spadae22/odoo,alexcuellar/odoo,CatsAndDogsbvba/odoo,Adel-Magebinary/odoo,NeovaHealth/odoo,Nowheresly/odoo,funkring/fdoo,makinacorpus/odoo,dfang/odoo,NeovaHealth/odoo,storm-computers/odoo,spadae22/odoo,Elico-Corp/odoo_OCB,odootr/odoo,NeovaHealth/odoo,tvibliani/odoo,synconics/odoo,OpenUpgrade/OpenUpgrade,leorochael/odoo,bplancher/odoo,hip-odoo/odoo,Daniel-CA/odoo,leorochael/odoo,NeovaHealth/odoo,diagramsoftware/odoo,Elico-Corp/odoo_OCB,OpenUpgrade/OpenUpgrade,odootr/odoo,datenbetrieb/odoo,tvibliani/odoo,odootr/odoo,Nowheresly/odoo,laslabs/odoo,CatsAndDogsbvba/odoo,Daniel-CA/odoo,alexcuellar/odoo,funkring/fdoo,Daniel-CA/odoo,alexcuellar/odoo,diagramsoftware/odoo,bplancher/odoo,glovebx/odoo,Daniel-CA/odoo,Daniel-CA/odoo,vnsofthe/odoo,spadae22/odoo,glovebx/odoo,Nowheresly/odoo,dfang/odoo,ehirt/odoo,makinacorpus/odoo,bplancher/odoo,CatsAndDogsbvba/odoo,ygol/odoo,storm-computers/odoo,laslabs/odoo,synconics/odoo,Nowheresly/odoo,ygol/odoo,vnsofthe/odoo,datenbetrieb/odoo,ygol/odoo,BT-ojossen/odoo,OpenUpgrade/OpenUpgrade,ehirt/odoo,diagramsoftware/odoo,hip-odoo/odoo,ehirt/odoo,leorochael/odoo,synconics/odoo,CatsAndDogsbvba/odoo,laslabs/odoo,odootr/odoo,spadae22/odoo,laslabs/odoo,ygol/odoo,datenbetrieb/odoo,NeovaHealth/odoo,OpenUpgrade/OpenUpgrade,synconics/odoo,BT-ojossen/odoo,glovebx/odoo,hip-odoo/odoo,datenbetrieb/odoo,glovebx/odoo,leorochael/odoo,CatsAndDogsbvba/odoo,ygol/odoo,makinacorpus/odoo,leorochael/odoo,vnsofthe/odoo,OpenUpgrade/OpenUpgrade,storm-computers/odoo,laslabs/odoo,bplancher/odoo,funkring/fdoo,dfang/odoo,laslabs/odoo,odootr/odoo,tvibliani/odoo,diagramsoftware/odoo,datenbetrieb/odoo,dfang/odoo,odootr/odoo,Adel-Magebinary/odoo,CatsAndDogsbvba/odoo,hip-odoo/odoo,OpenUpgrade/OpenUpgrade,BT-ojossen/odoo,ygol/odoo,Daniel-CA/odoo,NeovaHealth/odoo,tvibliani/odoo,funkring/fdoo,OpenUpgrade/OpenUpgrade