Yeet term-ansicolor and tins from test dependencies

I was trying to fix CI by pinning `term-ansicolor` to a specific
version, but Daniel pointed out that we don't even seem to use it
anywhere, so let's throw it (and its `tins` dependency) out.

Signed-off-by: Chris Sinjakli <chris@sinjakli.co.uk>

Author: Sinjo

Gemfile

@@ -9,6 +9,4 @@ group :test do
   gem 'rack-test'
   gem 'rake'
   gem 'rspec'
-  gem 'term-ansicolor'
-  gem 'tins'
 end