We can lower the eslint cyclomatic complexity threshold in some directories without adding eslint suppression comments in any .js source files. We need to specify the complexity rule in accessible/.eslintrc because it doesn't inherit the mozilla/recommended rules. eslint's default complexity threshold is 20.
Also bump the eslint-plugin-mozilla version because we modified the mozilla/recommended rules.
MozReview-Commit-ID: 57T4gAjPH7z
