[ruby/webrick] Only run test_big_bodies test on Ruby 2.5+
It was added after Ruby 2.5, and it looks like it never ran correctly on Ruby <2.5.
https://github.com/ruby/webrick/commit/65fb03cb6a
Added by jeremyevans (Jeremy Evans) about 5 years ago
[ruby/webrick] Only run test_big_bodies test on Ruby 2.5+
It was added after Ruby 2.5, and it looks like it never ran correctly
on Ruby <2.5.
https://github.com/ruby/webrick/commit/65fb03cb6a