Update src/routes/reference/components/error-boundary.mdx

Co-authored-by: Sarah <gerrardsarah@gmail.com>

Author: amirhhashemi

src/routes/reference/components/error-boundary.mdx

@@ -4,7 +4,7 @@ order: 5
 ---
 
 The `<ErrorBoundary>` component catches errors that occur during the rendering or updating of its children, and shows a fallback UI instead.
-That includes:
+This includes:
 
 - Errors that occur while rendering JSX.
 - Errors that occur within `createEffect`, `createMemo`, and other state management primitives.