Drop libtraprain-0-doc, not built anymore since Apertis v2021

Building libtraprain-0-doc requires hotdoc-0.8 which is unsupported after Apertis v2021. Keeping libtraprain-0-doc around here force us to whitelist this package, see infrastructure/dashboard!178 (comment 118460)

Signed-off-by: Dylan Aïssi dylan.aissi@collabora.com