Reduce number of lint rules in example app

[matejchalk]

The react-todos-app is used in E2E tests for testing ESLint plugin among others. But since a lot of recommended ESLint rules are included, the test snapshots are quite large and therefore less readable. Most of the rules pass anyway, so they don't give much data variety. So we could remove some passing rules from the ESLint config without losing any test coverage.