Allow ohai versions > 17 to be used

The restricton `< 17` was originally added by 2777c5b in
#1013 because `omnibus-toolchain`
was still shipping Ruby 2.6 at that time, and Ohai 17 required Ruby 17.
However, starting with
chef/omnibus-toolchain#153, `omnibus-toolchain`
is on Ruby 2.7+, and hence this restriction can be removed.

Signed-off-by: Balasankar "Balu" C <balasankar@gitlab.com>

omnibus.gemspec

@@ -25,7 +25,7 @@ Gem::Specification.new do |gem|
   gem.add_dependency "chef-cleanroom",   "~> 1.0"
   gem.add_dependency "ffi-yajl",         "~> 2.2"
   gem.add_dependency "mixlib-shellout",  ">= 2.0", "< 4.0"
-  gem.add_dependency "ohai",             ">= 15", "< 17"
+  gem.add_dependency "ohai",             ">= 15""
   gem.add_dependency "ruby-progressbar", "~> 1.7"
   gem.add_dependency "thor",             ">= 0.18", "< 2.0"
   gem.add_dependency "license_scout",    "~> 1.0"