Fix wording in Upgrade Guide

docs/v2/upgrade-guides/2.0.md

@@ -1001,7 +1001,7 @@ The following functions and properties were **removed from the codebase**, eithe
 - `get_url()` – use `{{ image.src }}` instead
 - `url()` – use `{{ image.src }}` instead
 - `$caption` property – use `caption()` method instead. You can still use `{{ image.caption }}` in Twig. In PHP `$image->caption` also still works because magic properties will automatically resolve to `$image->caption()`.
-- `is_image()` – without replacement. Timber now checks whether a post is an image if you use `Timber::get_post()` or `Timber::get_image()` and only returns an `Timber\Image` an object for attachments that are images.
+- `is_image()` – without replacement. Timber now checks whether a post is an image if you use `Timber::get_post()` or `Timber::get_image()` and only returns a `Timber\Image` object for attachments that are images.
 
 ### Timber\MenuItem