Fix eslint for newly added .lighthouserc

This MR fixes eslint errors on master (https://gitlab.com/gitlab-org/status-page/-/jobs/1019993174) such as:

$ vue-cli-service lint --no-fix
error: Filename '.lighthouserc.js' does not match the naming convention (filenames/match-regex) at .lighthouserc.js:1:1:
> 1 | module.exports = {
    | ^
  2 |   ci: {
  3 |     collect: {
  4 |       startServerCommand: "ENV=production yarn serve",
error: Replace `"ENV=production·yarn·serve"` with `'ENV=production·yarn·serve'` (prettier/prettier) at .lighthouserc.js:4:27:
  2 |   ci: {
  3 |     collect: {
> 4 |       startServerCommand: "ENV=production yarn serve",
    |                           ^
  5 |       url: ['http://localhost:8080'],
  6 |       settings: {chromeFlags: '--no-sandbox'},
  7 |     },
error: Replace `chromeFlags:·'--no-sandbox'` with `·chromeFlags:·'--no-sandbox'·` (prettier/prettier) at .lighthouserc.js:6:18:
  4 |       startServerCommand: "ENV=production yarn serve",
  5 |       url: ['http://localhost:8080'],
> 6 |       settings: {chromeFlags: '--no-sandbox'},
    |                  ^
  7 |     },
  8 |     upload: {
  9 |       target: 'temporary-public-storage',
3 errors found.
2 errors potentially fixable with the `--fix` option.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Started to fail after merging !212 (merged).