Log Message:
Update ruby-multi_json to 1.12.1.

1.12.1
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* [Prevent meory leak in \ 
OptionsCache](https://github.com/intridea/multi_json/commit/aa7498199ad272f3d4a13750d7c568a66047e2ee)

1.12.0
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* [Introduce global options cache to improve \ 
peroformance](https://github.com/intridea/multi_json/commit/7aaef2a1bc2b83c95e4208b12dad5d1d87ff20a6)