[DRE-maint] Bug#894305: package build-depends on legacy ruby2.3-dev

[Matthias Klose]

Package: src:ruby-debugger-ruby-core-source
Version: 1.3.8+ds-1
Severity: serious
Tags: sid buster patch

the package build-depends on legacy ruby2.3-dev which is going to be removed. Is
there are reason not to use the unversioned b-d?

patch at
http://launchpadlibrarian.net/362398716/ruby-debugger-ruby-core-source_1.3.8+ds-1_1.3.8+ds-1ubuntu1.diff.gz