remove unused abbrev dependency

[zvkemp]

It looks like the only usage of abbrev was removed in 9994c66.

[calebhearth]

FWIW, abbrev being around is causing errors that seem to be caused by Zeitwerk, but are actually coming from this gem:

/Users/caleb/.gem/ruby/2.6.10/gems/zeitwerk-2.6.12/lib/zeitwerk/kernel.rb:38: warning: abbrev was loaded from the standard library, but will no longer be part of the default gems since Ruby
 3.4.0. Add abbrev to your Gemfile or gemspec. Also contact author of zeitwerk-2.6.12 to add abbrev into its gemspec.    

❯ ag "require .abbrev." .gem                                                                                                                                          
.gem/ruby/3.3.0/gems/highline-2.1.0/lib/highline.rb                                                                                                                                          
17:require "abbrev"                                                                                                                                                                          
                                                                                                                                                                                             
.gem/ruby/3.2.2/gems/highline-2.1.0/lib/highline.rb                                                                                                                                          
17:require "abbrev"              

[abinoam]

Nice spot! Thank you very much both of you.
My bad for not checking its use before previous release.
I'll merge it and release it.

[abinoam]

Released 🚀

https://rubygems.org/gems/highline/versions/3.0.1