Revert "mark fluent-ffmpeg as external"

This reverts commit 74cd317.

Author: nicktrn

packages/build/src/extensions/core/ffmpeg.ts

@@ -24,13 +24,6 @@ export type FfmpegOptions = {
 export function ffmpeg(options: FfmpegOptions = {}): BuildExtension {
   return {
     name: "ffmpeg",
-    externalsForTarget(target) {
-      if (target === "dev") {
-        return [];
-      }
-
-      return ["fluent-ffmpeg"];
-    },
     onBuildComplete(context) {
       if (context.target === "dev") {
         return;