Resolve grammatical errors in examples (#65644)

## Description
I fixed grammatical errors in a few READMEs in the `example` directory.

---------

Co-authored-by: Sam Ko <sam@vercel.com>

examples/image-legacy-component/README.md

@@ -1,6 +1,6 @@
 # Legacy Image Component Example
 
-This example shows how to use the [Legacy Image Component in Next.js](https://nextjs.org/docs/api-reference/next/legacy/image) serve optimized, responsive images.
+This example shows how to use the [Legacy Image Component in Next.js](https://nextjs.org/docs/api-reference/next/legacy/image) to serve optimized, responsive images.
 
 The index page ([`pages/index.js`](pages/index.js)) has a couple images, one internal image and one external image. In [`next.config.js`](next.config.js), the `domains` property is used to enable external images. The other pages demonstrate the different layouts. Run or deploy the app to see how it works!
 

examples/with-react-ga4/README.md

@@ -2,8 +2,8 @@
 
 As of May 2023, [react-ga](https://github.com/react-ga/react-ga/issues/541) uses Universal Analytics which will stop processing new data starting July 2023. Until this is fixed, this example has been updated to use [react-ga4](https://github.com/codler/react-ga4) instead.
 
-This example shows the most basic way to use [react-ga4](https://github.com/codler/react-ga4) using custom [App](https://github.com/vercel/next.js#custom-app)
-component with NextJs. Modify `Tracking ID` in `utils/analytics.js` file for testing this example.
+This example shows the most basic way to use [react-ga4](https://github.com/codler/react-ga4) using a custom [App](https://github.com/vercel/next.js#custom-app)
+component with Next.js. Modify `Tracking ID` in `utils/analytics.js` file for testing this example.
 
 ## Deploy your own