fix(gatsby): Remove plugin configuration docs (#6246)

We want users to only use the `sentry.config.ts` method, not the plugin options method, so remove it from the docs. Version 7 has been out long enough that this should be safe to do.

Author: AbhiPrasad

src/platforms/javascript/guides/gatsby/index.mdx

@@ -22,19 +22,7 @@ yarn add @sentry/gatsby
 
 </Note>
 
-## Connecting the SDK to Sentry
-
-You can configure the SDK in one of two ways discussed below: by creating a configuration file, or defining the options along with the Gatsby configuration. If you define options in both places, the SDK will prioritize the `init` in the configuration file and ignore the options in the Gatsby configuration.
-
-### Sentry Configuration File
-
-<Note>
-
-The minimum version supporting the Sentry configuration file is `6.14.0`.
-
-</Note>
-
-Using a Sentry configuration file is the approach we recommend since it supports defining non-serializable options in the `init`. Note that you still need to include the plugin, even if you don't set any options.
+First add `@sentry/gatsby` as a plugin to your `gatsby-config.js`.
 
 ```javascript {filename:gatsby-config.js}
 module.exports = {
@@ -46,7 +34,7 @@ module.exports = {
 };
 ```
 
-Configure your `Sentry.init`:
+Then, configure your `Sentry.init`:
 
 ```javascript {filename:sentry.config.js}
 import * as Sentry from "@sentry/gatsby";
@@ -83,36 +71,3 @@ Sentry.init({
   // ...
 });
 ```
-
-### Gatsby Plugin Configuration
-
-Another alternative is to use Gatsby's [plugin configuration options](https://www.gatsbyjs.com/docs/how-to/plugins-and-themes/using-a-plugin-in-your-site/#using-plugin-configuration-options). While this keeps the SDK options with the plugin definition, it doesn't support non-serializable options like `integrations`, `transport`, `stackParser`,`beforeSend`, `beforeSendTransaction`, and `tracesSampler`.
-
-```javascript {filename:gatsby-config.js}
-module.exports = {
-  plugins: [
-    {
-      resolve: "@sentry/gatsby",
-      options: {
-        dsn: "___PUBLIC_DSN___",
-        tracesSampleRate: 1.0, // Adjust this value in production
-        // Cannot set any non-serializable options
-      },
-    },
-  ],
-};
-```
-
-With this approach, the SDK sets some options automatically based on environmental variables, but these can be overridden by setting custom options.
-
-`environment` (string)
-
-: Defaults to `process.env.NODE_ENV` or `development`
-
-`release` (string)
-
-: Defaults to certain environment variables based on the platform
-
-- GitHub Actions: `process.env.GITHUB_SHA`
-- Netlify: `process.env.COMMIT_REF`
-- Vercel: `process.env.VERCEL_GIT_COMMIT_SHA`