[Development] FYI: non-approvers may now stage/submit

[Oswald Buddenhagen]

moin,

it occurred to me that the inability of contributors to stage/submit
their own changes ( https://bugreports.qt-project.org/browse/QTQAINFRA-303 )
results merely from our stupidity, and not some technical problem. so
after consultation with sergio i just changed it. at least i think so. ^^

the only "danger" i forsee is mindless re-staging upon integration
failure. should this materialize, Measures Will Be Taken ™. but for the
time being CI is too unreliable anyway and *everybody* is re-staging
mindlessly ...

this also means that approvers have no excuse for being trigger-happy at
all any more. leave staging to the author - he typically knows best in
which order and when to submit stuff.

have fun