chore: fix assets bundling integ test (#35228)

In this test, the platform specified to bundle the asset is `linux/amd64`. But the image used doesn't specify any platform. This is causing the `integ.assets.bundling.docker-opts.ts` to fail with the message:

>Unable to find image 'cdk-66687611b68d3de0f92ed971e4c457e4828f2e0c877c8b1f5fab42ac3d2772ec:latest' locally
>docker: Error response from daemon: pull access denied for cdk-66687611b68d3de0f92ed971e4c457e4828f2e0c877c8b1f5fab42ac3d2772ec, repository does not exist or may require 'docker login'
>
>Run 'docker run --help' for more information

Add the platform to the build parameters of the Docker image.

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: otaviomacedo

packages/@aws-cdk-testing/framework-integ/test/aws-s3-assets/test/integ.assets.bundling.docker-opts.ts

@@ -9,7 +9,10 @@ const stack = new Stack(app, 'cdk-integ-assets-bundling-docker-opts');
 new assets.Asset(stack, 'BundledAsset', {
   path: path.join(__dirname, 'markdown-asset'), // /asset-input and working directory in the container
   bundling: {
-    image: DockerImage.fromBuild(path.join(__dirname, 'alpine-markdown')), // Build an image
+    // Build an image
+    image: DockerImage.fromBuild(path.join(__dirname, 'alpine-markdown'), {
+      platform: 'linux/amd64',
+    }),
     command: [
       'sh', '-c', `
         markdown index.md > /asset-output/index.html