Add Ruby 3.1 and head to tested versions (#182)

* Add Ruby 3.1 and head to tested versions

* Fix spec for Ruby 3.1

Ruby 3.1's error message becomes more verbose. Properly loose the
expectation to have the spec passed for all Ruby versions.

.github/workflows/ruby.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ['2.6', '2.7', '3.0']
+        ruby-version: ['2.6', '2.7', '3.0', '3.1', 'head']
 
     steps:
     - uses: actions/checkout@v2

spec/helper_spec.rb

@@ -33,7 +33,7 @@ describe OneGadget::Helper do
 
   it 'url_request' do
     val = :val
-    expect { hook_logger { val = described_class.url_request('oao') } }.to output(<<-EOS).to_stdout
+    expect { hook_logger { val = described_class.url_request('oao') } }.to output(include(<<-EOS)).to_stdout
 [OneGadget] undefined method `request_uri' for #<URI::Generic oao>
     EOS
     expect(val).to be_nil