- Use `Node.TEXT_NODE` rather than a magical constant, in `TextHighlighter._convertMatches`, to improve readability. According to MDN, this has been supported since "forever": https://developer.mozilla.org/en-US/docs/Web/API/Node/nodeType#browser_compatibility
- Remove the `pageIdx`-property, on `TextLayerBuilder`-instances, since the re-factoring in PR 13908 meant that it's now unused.
- Remove the `matches`-property, on `TextLayerBuilder`-instances, since the re-factoring in PR 13908 meant that it's now unused.