fix(cli): failure to load malformed YAML is swallowed (#19338)

For some reason, we are falling back to reading JSON when loading YAML fails.

Since YAML is a superset of JSON, the only reason errors would occur because the YAML is not valid, in which case we shouldn't do this catch at all.

Fixes #19335.

----

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

packages/aws-cdk/lib/serialize.ts

@@ -12,12 +12,7 @@ export function toYAML(obj: any): string {
  * Parse either YAML or JSON
  */
 export function deserializeStructure(str: string): any {
-  try {
-    return yaml_cfn.deserialize(str);
-  } catch (e) {
-    // This shouldn't really ever happen I think, but it's the code we had so I'm leaving it.
-    return JSON.parse(str);
-  }
+  return yaml_cfn.deserialize(str);
 }
 
 /**