Pin merge 1.2.1 (#393)
Pin merge 1.2.1 (#393)

Summary:
This addresses [CVE-2018-16469](https://nvd.nist.gov/vuln/detail/CVE-2018-16469).
Pull Request resolved: https://github.com/facebook/flipper/pull/393

Reviewed By: danielbuechele

Differential Revision: D14342214

Pulled By: passy

fbshipit-source-id: fc5c7a552f413f54f31f3c2cfb12fd511ecbd35e

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