Upgrade commonmark to 0.10.0

The version of commonmark must be aligned with the version used in
core gitiles 0.2-5, which is 0.10.0 [1].

[1] https://gerrit.googlesource.com/gitiles/+/v0.2-5/WORKSPACE#54

Change-Id: I3046d952f74241df97876167eef63f68338e4b45
1 file changed