Fix Json.stringify parameters for use with newer versions of wing compiler

[whummer]

Fix Json.stringify(..) parameters in sample, for use with newer versions of wing compiler:

$ wing compile --target tf-aws voting-app/main.w

error: Expected type to be "JsonStringifyOptions?", but got "num" instead
    --> voting-app/main.w:232:28
    |
232 |   log(Json.stringify(body, 2));
    |                            ^ Expected type to be "JsonStringifyOptions?", but got "num" instead

wing version:

$ wing --version
0.26.7

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Another alternative would be to remove the parameter altogether, to make the sample code backward-compatible with older wing versions. Not sure what would be preferable from your perspective?

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/cc @Chriscbr @skorfmann

[Chriscbr]

Thanks @whummer!