Remove invalid react property i18n config (#54)

## Ticket

resolves #51 

## Changes
Removed the `react` property from the `i18n` property in
`next-i18next.config.json`.

## Context for reviewers
When running the build, prior to this change, the output would show:

```
warn  - Invalid next.config.js options detected: 
  - The value at .i18n has an unexpected property, react, which is not in the list of allowed properties (defaultLocale, domains, localeDetection, locales).

See more info here: https://nextjs.org/docs/messages/invalid-next-config
```

The problematic config looked like this:

```
    react: {
      // Add support for <em>.
      // See https://react.i18next.com/latest/trans-component#using-for-less-than-br-greater-than-and-other-simple-html-elements-in-translations-v-10-4-0
      transKeepBasicHtmlNodesFor: ["br", "strong", "i", "p", "em"],
    },
```

I'm not aware of a good reason for that setting to be set generally in
the template; the link in the comment was outdated, so the anchor it
tried to connect to no longer exists, but at the top of that page, it
says "the truth is: in most cases you don't even need it" in reference
to the `Trans` component the `transKeepBasicHtmlNodesFor` setting
connects to. There may be reason for an individual application to use
that setting, but I don't think the template needs to have it by
default, and either way, the option was being set improperly anyway, so
I opted to remove the `react` property altogether.

## Testing
Ran `npm run test` and `npm run dev` and everything seems to work as
normal. Running `npm run build` no longer shows the error message
referenced in the issue.

Author: jimmyfagan

app/next-i18next.config.js

@@ -2,11 +2,6 @@ module.exports = {
   i18n: {
     defaultLocale: "en",
     locales: ["en", "es"],
-    react: {
-      // Add support for <em>.
-      // See https://react.i18next.com/latest/trans-component#using-for-less-than-br-greater-than-and-other-simple-html-elements-in-translations-v-10-4-0
-      transKeepBasicHtmlNodesFor: ["br", "strong", "i", "p", "em"],
-    },
   },
   // Locale resources are loaded once when the server is started, which
   // is good for production but not ideal for local development. Show