Fix dataset in compliance test

[jsoriano]

- is not allowed in datasets since https://github.com/elastic/kibana/pull/182925

Fixes issue found in https://buildkite.com/elastic/package-spec/builds/664#018f9c74-ef57-4b56-b8ad-9b390d847bae:

Step a policy is created with "basic_input" package, "test" template, "test" input, "logfile" input type and dataset "spec.input-test": failed to create package policy: request failed with status 400, body: {"statusCode":400,"error":"Bad Request","message":"Package policy is invalid: inputs.logfile.streams.basic_input.test.vars.data_stream.dataset: Dataset contains invalid characters"}

We may consider adding validation for these fields in the test config files as a follow up.

[elasticmachine]

:green_heart: Build Succeeded

• Buildkite Build
• Commit: 408f0529c0ddf05275735940541e1db59c40383b

cc @jsoriano