Update incremental-static-regeneration.md (#37159)

I couldn't understand well this sentence at the first time of reading as a non native english speaker. I think 'that' is needed here.



## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [x] Make sure the linting passes by running `yarn lint`

docs/basic-features/data-fetching/incremental-static-regeneration.md

@@ -139,7 +139,7 @@ $ next build
 $ next start
 ```
 
-Then, you are able to validate static pages are successfully revalidated.
+Then, you can confirm that static pages have successfully revalidated.
 
 ## Error handling and revalidation