chore: remove dependency on tv4-formats

[sarfata]

TV4-Format provides some JSON validation helper for common string
formats. It was loaded only when validating the full model (not delta)
and all the tests run without it so I propose we remove it.

Reason for me looking into this is that this library causes problem with
webpack because of a heuristic they use to require one of their
dependency. This is a known issue that they have fixed in a later
version and I have confirmed that upgrading the package fixes the issue
for us too. However, if we do not use the library I think it's better to
completely remove it.

For more info: ikr/tv4-formats@61450dc

[sarfata]

ping? @tkurki are you ok merging this?

[tkurki]

all the tests run without it does not mean that it is not used: try mangling a timestamp in one of the test full files and run the tests - they will fail. This dependency adds validation of date-time JSON Schema data type that is in use in the schema.

Options on how to move forward:

• update to the current version of tv4 & formats
• switch to a better validation tool Switch to better validation tool #246 that supports checking for unknown properties

Then there is the issue of separating the schema js API #435 (including validation) from the actual schema data itself, versioning them separately. Then we would have the option two npm packages, one with schema data and js access to it and another for validation, versioned independently.

[sarfata]

@tjkurki Sorry about that. My bad.

Pushed #501 instead. Hopefully this works for you.