chore: suppress a type error (#31751)

Not sure how this is not causing a compilation error at CDK build time, but it's a red underline in my IDE and a compilation error in the new CLI repo.

Fixing it.

----

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

tools/@aws-cdk/node-bundle/src/api/bundle.ts

@@ -414,7 +414,7 @@ export class Bundle {
       throw new Error(`Multiple versions detected for external dependency: ${name} (${Array.from(versions).join(',')})`);
     }
 
-    return versions.values().next().value;
+    return versions.values().next().value!;
   }
 
   private closestPackagePath(fdp: string): string {