Fix typo in Workers example

[irvinebroque]

Seems like examples here aren't autogen

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[jacobbednarz]

yep, v4.x does not have autogenerated examples. 5.x onwards is.

two things with this:

1. this is the legacy resource (worker_script, missing the s in workers) and it's around for documentation purposes if folks are still using it.
2. if we don't want this, we need to update https://github.com/cloudflare/terraform-provider-cloudflare/blob/master/examples/resources/cloudflare_worker_script/resource.tf as the docs directory is generated from the schema + examples to build these pages.