Switch jsoncpp DEPS to github mirror

This change should be no-op.  It simply changes the sha1
for jsoncpp to match the commit in the github repo rather
than the git-svn mirror we previously used.  The sha1
differs simply because the git-svn metadata was not used
when they migrated to github. The tree contents are
identical (the two commits have the same tree sha1).

BUG=472809

Review URL: https://codereview.chromium.org/1069163002

Cr-Original-Commit-Position: refs/heads/master@{#324477}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 12f9e9d69d223afd5c30dad8934932aefdeba35e
2 files changed