Update with-react-bootstrap to be Turbopack compatible (#62773)

## What?

This example used the legacy `~` operator which is no longer required in
latest webpack.

In case you land here trying Turbopack and running into the can't
resolve error this will be useful to know:

If you still need `~` it can be aliased using the `resolveAlias` option
in Turbopack:


```
module.exports = {
  experimental: {
    turbo: {
      resolveAlias: {
        '~*': '*',
      },
    },
  },
}
```

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Closes NEXT-2673

examples/with-react-bootstrap/pages/_app.jsx

@@ -1,3 +1,4 @@
+import "bootstrap/dist/css/bootstrap.min.css";
 import "../style/index.css";
 
 export default function MyApp({ Component, pageProps }) {

examples/with-react-bootstrap/style/index.css

@@ -1,6 +1,3 @@
-/* ensure all pages have Bootstrap CSS */
-@import "~bootstrap/dist/css/bootstrap.min.css";
-
 .md-container {
   max-width: 800px;
   padding-top: 2rem;

examples/with-reactstrap/pages/_app.jsx

@@ -1,3 +1,5 @@
+import "bootstrap/dist/css/bootstrap.min.css";
+
 import "../styles/index.css";
 
 export default function MyApp({ Component, pageProps }) {

examples/with-reactstrap/styles/index.css

@@ -1,6 +1,3 @@
-/* ensure all pages have Bootstrap CSS */
-@import "~bootstrap/dist/css/bootstrap.min.css";
-
 .md-container {
   max-width: 800px;
   padding-top: 2rem;