fix(tooling): update vscode devcontainer image (#18455)

The `latest` tag of the `jsii/superchain` image has long been deprecated. This aligns the devcontainer image with the one used for gitpod.


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.devcontainer.json

@@ -1,8 +1,8 @@
 {
     "name": "Dev Container Definition - AWS CDK",
-    "image": "jsii/superchain",
+    "image": "jsii/superchain:1-buster-slim",
     "postCreateCommand": "yarn build --skip-test --no-bail --skip-prereqs --skip-compat",
     "extensions": [
         "[email protected]"
     ]
-}
+}