osmocom_build_deps.yml: add inkscape

osmo-gsm-manuals needs inkscape to handle svgs. Not all osmo-* projects
are building in docker, so make sure it is also installed on the build
slaves directly.

Related: OS#4314
Change-Id: I63460336d2c4a7594ec9c5c9b60a3d43f0d157aa
1 file changed