Remove the warning for build worker when custom webpack present (#60820)

Drop the warning of build worker due to the common usage of custom
webpack

Closes NEXT-2148

errors/webpack-build-worker-opt-out.mdx

@@ -1,15 +0,0 @@
----
-title: Webpack Build Worker automatic opt-out
----
-
-## Webpack Build Worker Opt-out
-
-#### Why This Error Occurred
-
-The Next.js config contains custom webpack configuration, as a result, the webpack build worker optimization was disabled.
-
-The webpack build worker optimization helps alleviate memory stress during builds and reduce out-of-memory errors although some custom configurations may not be compatible.
-
-#### Possible Ways to Fix It
-
-You can force enable the option by setting `config.experimental.webpackBuildWorker: true` in the config.

packages/next/src/build/index.ts

@@ -1365,14 +1365,6 @@ export default async function build(
       )
       nextBuildSpan.setAttribute('use-build-worker', String(useBuildWorker))
 
-      if (
-        config.webpack &&
-        config.experimental.webpackBuildWorker === undefined
-      ) {
-        Log.warn(
-          'Custom webpack configuration is detected. When using a custom webpack configuration, the Webpack build worker is disabled by default. To force enable it, set the "experimental.webpackBuildWorker" option to "true". Read more: https://nextjs.org/docs/messages/webpack-build-worker-opt-out'
-        )
-      }
       if (
         !useBuildWorker &&
         (runServerAndEdgeInParallel || collectServerBuildTracesInParallel)