remove obsolete list upgrade code for bit structs
remove obsolete list upgrade code for bit structs

pjulien/capnproto,jparyani/capnproto,mologie/capnproto,bryce-gibson/capnproto,geofft/capnproto,ocdtrekkie/capnproto,bryce-gibson/capnproto,kamalmarhubi/capnproto,Fraser999/capnproto,mrdomino/capnproto,rcrowder/capnproto,a-richardson/capnproto,pjulien/capnproto,pjulien/capnproto,zarvox/capnproto,johnkdoe/capnproto,ocdtrekkie/capnproto,maurer/capnproto,martindale/capnproto,mologie/capnproto,geofft/capnproto,zarvox/capnproto,bryce-gibson/capnproto,MarPiRK/capnproto,maurer/capnproto,geofft/capnproto,rcrowder/capnproto,maurer/capnproto,rcrowder/capnproto,joliss/capnproto,jparyani/capnproto,khklau/capnproto,hntrmrrs/capnproto,a-richardson/capnproto,bsn069/capnproto,kamalmarhubi/capnproto,khklau/capnproto,kamalmarhubi/capnproto,MarPiRK/capnproto,Fraser999/capnproto,ligzy/capnproto,joliss/capnproto,hntrmrrs/capnproto,a-richardson/capnproto,johnkdoe/capnproto,bsn069/capnproto,ocdtrekkie/capnproto,Fraser999/capnproto,nagyistoce/capnproto,vladon/capnproto,mrdomino/capnproto,zarvox/capnproto,nagyistoce/capnproto,martindale/capnproto,martindale/capnproto,joliss/capnproto,modulexcite/capnproto,modulexcite/capnproto,bsn069/capnproto,modulexcite/capnproto,vladon/capnproto,nagyistoce/capnproto,jparyani/capnproto,MarPiRK/capnproto,ligzy/capnproto,mologie/capnproto,johnkdoe/capnproto,hntrmrrs/capnproto,vladon/capnproto,ligzy/capnproto,mrdomino/capnproto,khklau/capnproto