[BUG] `--union-enums` cli flag no longer works in 13.0.28

[mariansimecek]

Running command:
swagger-typescript-api generate --path [REDACTED] --output src/app/modules/_models/generated --no-client --extract-request-params --union-enums --extract-response-body --extract-response-error --add-readonly --name types.generated.ts

This always generates TypeScript enums instead of unions, regardless of the --union-enums flag. This works fine in version 13.0.27.

[smorimoto]

See #1141. The --union-enums flag itself was a bug...