[DRE-maint] Bug#1053465: unicorn: Unnecessary Build-Depends on quilt

[Gioele Barabucci]

Package: src:unicorn
Version: 6.1.0-2
Tags: patch

Dear maintainers,

the `unicorn` package does not need to Build-Depends on `quilt`. 
`dpkg-source` built-in support for quilt patches (already integrated in 
the standard `dh` pipeline) is enough.

A patch to fix this issue is included in the following MR:
https://salsa.debian.org/ruby-team/unicorn/-/merge_requests/2

--
Gioele Barabucci