build(deps): Bump libmozdata from 0.1.66 to 0.1.68 in /bot (#501)

Bumps [libmozdata](https://github.com/mozilla/libmozdata) from 0.1.66 to 0.1.68.
- [Release notes](https://github.com/mozilla/libmozdata/releases)
- [Commits](mozilla/libmozdata@v0.1.66...v0.1.68)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

bot/requirements.txt

@@ -1,6 +1,6 @@
 -e ../tools #egg=code-coverage-tools
 google-cloud-storage==1.27.0
-libmozdata==0.1.66
+libmozdata==0.1.68
 pytoml==0.1.21
 pytz==2019.3
 pyyaml==5.3.1