[Sync EN] image: Fix examples and description (#5442)

Commit: `https://github.com/php/doc-en/commit/d56953fc8d508615279a2220f21d7fb6c3298417`
PR: `https://github.com/php/doc-en/pull/5442`

**Archivos ES a actualizar**
- `reference/image/functions/imagedashedline.xml`
- `reference/image/functions/imagerectangle.xml`
- `reference/image/functions/imagesetbrush.xml`
- `reference/image/functions/imagesetthickness.xml`

