arg-cache: Use BoxedInTransferNone::release for GBytesInTransferNone::release

GBytes parameters in "transfer none" mode needs to be released after the
function returns, otherwise its reference count will be incremented even
if the callee doesn't own the reference, causing a memory leak. Fix this
by using BoxedInTransferNone::release instead of BoxedIn::release which is
a no-op.

Fixes GNOME/gnome-shell#5501
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