build(deps): bump libmozevent from 1.1.6 to 1.1.9 in /events

Bumps [libmozevent](https://github.com/mozilla/libmozdata) from 1.1.6 to 1.1.9.
- [Release notes](https://github.com/mozilla/libmozdata/releases)
- [Commits](https://github.com/mozilla/libmozdata/commits)

---
updated-dependencies:
- dependency-name: libmozevent
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

events/requirements.txt

@@ -1,2 +1,2 @@
 -e ../tools #egg=code-coverage-tools
-libmozevent==1.1.6
+libmozevent==1.1.9