[rubygems/rubygems] fix `@license` typo preventing licenses from being correctly unmarshalled

https://github.com/rubygems/rubygems/commit/d6ba7ef79f

lib/rubygems/specification.rb

@@ -1318,7 +1318,7 @@ class Gem::Specification < Gem::BasicSpecification
     spec.instance_variable_set :@has_rdoc,                  array[15]
     spec.instance_variable_set :@new_platform,              array[16]
     spec.instance_variable_set :@platform,                  array[16].to_s
-    spec.instance_variable_set :@license,                   array[17]
+    spec.instance_variable_set :@licenses,                  [array[17]]
     spec.instance_variable_set :@metadata,                  array[18]
     spec.instance_variable_set :@loaded,                    false
     spec.instance_variable_set :@activated,                 false

test/rubygems/test_gem_safe_marshal.rb

@@ -305,6 +305,18 @@ class TestGemSafeMarshal < Gem::TestCase
     end
   end
 
+  def test_gem_spec_unmarshall_license
+    spec = Gem::Specification.new do |s|
+      s.name = "hi"
+      s.version = "1.2.3"
+      s.license = "MIT"
+    end
+
+    unmarshalled_spec = Gem::SafeMarshal.safe_load(Marshal.dump(spec))
+
+    assert_equal ["MIT"], unmarshalled_spec.license
+  end
+
   def test_gem_spec_disallowed_symbol
     e = assert_raise(Gem::SafeMarshal::Visitors::ToRuby::UnpermittedSymbolError) do
       spec = Gem::Specification.new do |s|