cockpit-po-plugin: fix indentation in header output
cockpit-po-plugin: fix indentation in header output

Make a minor tweak to the indentation of the declaration of the
'plural-forms' lambda in the output.

This is trivial and silly, but it's necessary to preserve the property
that the following commits don't make any changes to the output format.

cockpit-project/cockpit,mvollmer/cockpit,martinpitt/cockpit,mvollmer/cockpit,cockpit-project/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,mvollmer/cockpit,mvollmer/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,martinpitt/cockpit