chore: continue support for ruby < 3.0

Signed-off-by: Sonu Saha <sonu.saha@progress.com>

chef-zero.gemspec

@@ -16,7 +16,11 @@ Gem::Specification.new do |s|
   # Note: 7.1.0 does not defaults its cache_format_version to 7.1 but 6.1 instead which gives deprecation warnings
   # Remove the version constraint when we can upgrade to 7.1.1 post stable release of Activesupport 7.1
   # Similar issue with 7.0 existed: https://github.com/rails/rails/pull/45293
-  s.add_dependency "activesupport", "~> 7.0", "< 7.1"
+  if RUBY_VERSION >= '3.0'
+    s.add_dependency "activesupport", "~> 7.0", "< 7.1"
+  else
+    s.add_dependency "activesupport", "~> 6.1"  # Pin for Ruby 2.6 support
+  end
   s.add_dependency "mixlib-log", ">= 2.0", "< 4.0"
   s.add_dependency "hashie", ">= 2.0", "< 5.0"
   s.add_dependency "uuidtools", "~> 2.1"