build(deps-dev): bump eslint-plugin-mozilla in /frontend

Bumps [eslint-plugin-mozilla](http://firefox-source-docs.mozilla.org/tools/lint/linters/eslint-plugin-mozilla.html) from 2.9.1 to 2.9.2.

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]