Fix CI for Ruby 3.4

In Ruby 3.4, Hash#inspect rendering have been changed:
https://bugs.ruby-lang.org/issues/20433

Some tests depend on the way hashes are serialized, so instead of
hardcoding them, ask the test suite to do it for us and use that to
assert the right value is passed around in tests.

Author: smortex

spec/facter/facter_spec.rb

@@ -598,7 +598,7 @@ def stub_no_fact
       context 'when exception and message are hashes' do
         let(:message) { { 'a': 1 } }
         let(:exception) { { 'b': 2 } }
-        let(:expected_message) { '{:a=>1}' }
+        let(:expected_message) { { a: 1 }.to_s }
 
         it_behaves_like 'when exception param is not an exception'
       end
@@ -682,7 +682,7 @@ def stub_no_fact
       context 'when exception and message are hashes' do
         let(:message) { { 'a': 1 } }
         let(:exception) { { 'b': 2 } }
-        let(:expected_message) { '{:a=>1}' }
+        let(:expected_message) { { a: 1 }.to_s }
 
         it_behaves_like 'when exception param is not an exception'
       end
@@ -808,7 +808,7 @@ def stub_no_fact
     end
 
     it 'when message is a hash' do
-      expect(logger).to receive(:warn).with('{:warn=>"message"}')
+      expect(logger).to receive(:warn).with({ warn: 'message' }.to_s)
 
       Facter.warn({ warn: 'message' })
     end