ci-license-scan: Workaround invalid copyright

When ci-license-scan tries to fill copyright information from d/copyright
it includes \n if they are present in copyright information. If later,
there is copyright data, the \n is placed in the middle creating an invalid
copyright file.

To overcome this issue, strip \n from the copyright.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>
Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>