pybind/mgr: Fix missing empty lines in mgr_module.py

pybind/mgr: Fix missing empty lines in mgr_module.py

The inline function documentation needs an empty
line between description and metadata.
Otherwise automethod from docs renders the metadata
as text together with the description instead of
rendering it as function metadata, e.g. parameters
and return value.

Signed-off-by: Ville Ojamo <14869000+bluikko@users.noreply.github.com>