Disable spec of pattern matching is experimental since 3.1

spec/ruby/language/pattern_matching_spec.rb

@@ -41,6 +41,7 @@ ruby_version_is "2.7" do
     end
 
     describe "warning" do
+      ruby_version_is ""..."3.1" do
         before :each do
           ruby_version_is ""..."3.0" do
             @src = 'case [0, 1]; in [a, b]; end'
@@ -61,6 +62,7 @@ ruby_version_is "2.7" do
           -> { eval @src }.should complain(/pattern matching is experimental, and the behavior may change in future versions of Ruby!/i)
         end
       end
+    end
 
     it "binds variables" do
       eval(<<~RUBY).should == 1