spec: Move RequestName API description to list of methods

spec: Move RequestName API description to list of methods

Tom Gundersen pointed out that RequestName, ReleaseName and
ListQueuedOwners were documented in their own section instead of being
put together with the other method calls, which makes it more difficult
to apply changes consistently across all methods.

I'm moving them one at a time to make the changes reviewable, since
the diff resulting from moving all three as a unit is too large to
review sensibly.

Signed-off-by: Simon McVittie <smcv@collabora.com>