Janitorial: Fix all ESLint errors

In #11095 we disabled bunch of rules due to fixing complexity of these errors. We should re-visit these rules and fix issues incrementally. Or just ignore them :)

List of disabled rules:

```
"wpcalypso/redux-no-bound-selectors": 0,
"jsx-a11y/anchor-has-content": 0,
"react/no-string-refs": 0,
"jsx-a11y/anchor-is-valid": 0,
```

Start by locating the ESLint configuration changed in #11095 and review the four disabled rules: redux-no-bound-selectors, anchor-has-content, react/no-string-refs, and anchor-is-valid. Trace the reported violations incrementally across the project, then verify that the rules can be re-enabled without unresolved ESLint errors.

Written by the indexing model from the issue text.