Fix diffing spec on jruby

spec/rspec/mocks/diffing_spec.rb

@@ -1,4 +1,5 @@
 require "spec_helper"
+require "pp"
 
 RSpec.describe "Diffs printed when arguments don't match" do
   before do
@@ -128,11 +129,12 @@ def self.name
         end.new
 
         collab_inspect = collab.inspect
+        collab_pp = PP.pp(collab, "").strip
 
         expect(d).to receive(:foo).with(collab)
         expect {
           d.foo([:a, :b])
-        }.to fail_with("Double \"double\" received :foo with unexpected arguments\n  expected: (#{collab_inspect})\n       got: ([:a, :b])\nDiff:\n@@ -1,2 +1,2 @@\n-[#{collab_inspect}]\n+[[:a, :b]]\n")
+        }.to fail_with("Double \"double\" received :foo with unexpected arguments\n  expected: (#{collab_inspect})\n       got: ([:a, :b])\nDiff:\n@@ -1,2 +1,2 @@\n-[#{collab_pp}]\n+[[:a, :b]]\n")
         reset d
       end
     end