[Pkg-chromium-maint] Bug#855529: chromium-widevine: dbgsym package in contrib causes src package to also go into contrib

[Michael Gilbert]

package: chromium-widevine
severity: serious
version: 55.0.2883.75-6

Just like #824169, the contrib dbgsym binary package causes the source
package to be duplicated in contrib.

Best wishes,
Mike