Normalize test for ruby-head compat

.github/workflows/liquid.yml

@@ -14,7 +14,7 @@ jobs:
           - { ruby: 3.0, allowed-failure: false } # minimum supported
           - { ruby: 3.2, allowed-failure: false }
           - { ruby: 3.3, allowed-failure: false } # latest
-          - { ruby: ruby-head, allowed-failure: true }
+          - { ruby: ruby-head, allowed-failure: false }
     name: Test Ruby ${{ matrix.entry.ruby }}
     steps:
       - uses: actions/checkout@v3

test/integration/standard_filter_test.rb

@@ -32,7 +32,7 @@ class TestDrop < Liquid::Drop
   attr_reader :value
 
   def registers
-    { @value => @context.registers[@value] }
+    "{#{@value.inspect}=>#{@context.registers[@value].inspect}}"
   end
 end