tools: update dotfile whitelist in .gitignore

.eslintrc was renamed in #7699 to .eslintrc.yaml.

PR-URL: https://github.com/nodejs/node/pull/12116
Refs: https://github.com/nodejs/node/pull/7699


Reviewed-By: Claudio Rodriguez <cjrodr@yahoo.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>