NPE: Fix umd package reference in es6 build command (#16746)

Looks like the initial changes for NPE the umd package got referenced in
the es6 build command. Quick fix for this.

Author: ryantrem

package.json

@@ -65,7 +65,7 @@
         "build:source": "tsc -b ./tsconfig.devpackages.json",
         "build:source:lts": "npx nx run-many --target=compile --projects=@lts/core,@lts/gui,@lts/loaders,@lts/materials,@lts/post-processes,@lts/procedural-textures,@lts/serializers --parallel=1",
         "build:umd": "nx run-many --target=build --parallel --maxParallel=6 --projects=babylonjs,babylonjs-gui,babylonjs-inspector,babylonjs-loaders,babylonjs-materials,babylonjs-serializers,babylonjs-post-process,babylonjs-procedural-textures,babylonjs-node-editor,babylonjs-node-geometry-editor,babylonjs-node-render-graph-editor,babylonjs-node-particle-editor,babylonjs-gui-editor,babylonjs-ktx2decoder,babylonjs-accessibility,babylonjs-addons",
-        "build:es6": "nx run-many --target=build --parallel --maxParallel=6 --projects=@babylonjs/core,@babylonjs/gui,@babylonjs/loaders,@babylonjs/materials,@babylonjs/serializers,@babylonjs/post-processes,@babylonjs/procedural-textures,@babylonjs/node-editor,@babylonjs/node-geometry-editor,@babylonjs/node-render-graph-editor,babylonjs-node-particle-editor,@babylonjs/inspector,@babylonjs/gui-editor,@babylonjs/viewer,@babylonjs/shared-ui-components,@babylonjs/addons,@babylonjs/accessibility,@babylonjs/ktx2decoder",
+        "build:es6": "nx run-many --target=build --parallel --maxParallel=6 --projects=@babylonjs/core,@babylonjs/gui,@babylonjs/loaders,@babylonjs/materials,@babylonjs/serializers,@babylonjs/post-processes,@babylonjs/procedural-textures,@babylonjs/node-editor,@babylonjs/node-geometry-editor,@babylonjs/node-render-graph-editor,@babylonjs/node-particle-editor,@babylonjs/inspector,@babylonjs/gui-editor,@babylonjs/viewer,@babylonjs/shared-ui-components,@babylonjs/addons,@babylonjs/accessibility,@babylonjs/ktx2decoder",
         "watch:shaders": "build-tools -c build-shaders --global --watch",
         "watch:assets": "build-tools -c pa --global --watch",
         "watch:source:dev": "tsc -b ./tsconfig.devpackages.json -w",