don't force strscan 3.1

Gemfile

@@ -25,5 +25,4 @@ group :test do
   gem 'rubocop-performance', require: false
 end
 
-gem "strscan", ">= 3.1"
 gem "lru_redux"

liquid.gemspec

@@ -30,6 +30,7 @@ Gem::Specification.new do |s|
 
   s.add_dependency("strscan")
   s.add_dependency("bigdecimal")
+  s.add_dependency("lru_redux")
 
   s.add_development_dependency('rake', '~> 13.0')
   s.add_development_dependency('minitest')