global: Remove managesieve_ event field prefixes

src/managesieve/cmd-deletescript.c

src/managesieve/cmd-getscript.c

src/managesieve/cmd-havespace.c

src/managesieve/cmd-putscript.c

src/managesieve/cmd-renamescript.c

src/managesieve/cmd-setactive.c

src/managesieve/managesieve-client.c