recipes-plasma: Add gettext-native as a dependency

Summary:
Following what was done in OE-core with patch:

atk: add explicit gettext-native dependency

we need to explicitly specify gettext-native as a dependency as the gettext
class reduces dependencies in native builds.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

Reviewers: vkrause

Reviewed By: vkrause

Differential Revision: https://phabricator.kde.org/D15003