[DRE-maint] Bug#1063658: drop snowlow-tracker orig tar

[Pirate Praveen]

Package: gitlab
Version: 16.6.6-3
Severity: wishlist

snowplow-tracker orig.tar can be removed now, this was included because 
snowplow-tracker was in vendor in a generated form so providing the 
corresponding source was required to satisfy dfsg. Now snowplow-tracker 
is available from npmjs.com and covered by yarn install in postinst.