Set uriOrEmpty from oneOf to anyOf for compatibility with validators that do not implement format uri

[kofalt]

From the spec:

JSON Schema implementations are not required to implement this part of the specification, and many of them do not.

If a validator does not implement "format": "uri", validation will fail because oneOf will be matched by both clauses. This changes it for anyOf, which will have no effect on complete parsers and be compatible with incomplete ones.

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Is this a semantic or operational change? If so:

• [x] Increment the version in spec/readme.md
• [x] After merge, tag the version and update the release page

[kofalt]

Very trivial change so merging to move this forward.