When faking data, it is useful if `json.Number` is faked with a number, otherwise json marshalling fails later with `"test string" is not a number`.

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Related to #462 and also #477.
Two reasons for this change:
1. We shouldn't be using `codes.Internal` as it's generated internally by gRPC so we won't be able to distinguish between gRPC protocol errors and application level errors, see https://github.com/grpc/grpc-go/blob/eeb9afa1f6b6388152955eeca8926e36ca94c768/codes/codes.go#L166.
2. We don't really do anything with the code at the moment, it's only printed in a confusing way (see #477)

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🤖 I have created a release *beep* *boop*
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## [1.12.0](v1.11.2...v1.12.0) (2022-12-11)


### Features

* Add handling for json.Number in faker ([#481](#481)) ([ad20787](ad20787))


### Bug Fixes

* Allow both 'yml' and 'yaml' extensions ([#476](#476)) ([52c4c56](52c4c56))
* **errors:** Remove usage of `codes.Internal` ([#485](#485)) ([62692b9](62692b9))

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