fix: Improve SortContent performance on large contracts (#538)

Whenever `order_verifiable_content` was called on `interactions` or
`messages` each item was serialized to json multiple times. WIth
`sort_by` each iteam is serialized once.

Flamegraph shows that this change intoduce a drop of SortContent#call
percentage in PactContentDiff.to_text call from 30% to 17%.

lib/pact_broker/pacts/sort_content.rb

@@ -34,7 +34,7 @@ def self.order_verifiable_content probably_array
         # You never can tell what people will do...
         if probably_array.is_a?(Array)
           array_with_ordered_hashes = order_hash_keys(probably_array)
-          array_with_ordered_hashes.sort{ |a, b| a.to_json <=> b.to_json }
+          array_with_ordered_hashes.sort_by(&:to_json)
         else
           probably_array
         end