doc: fix createwallet positional example, descriptors must be true #36460

The createwallet example in doc/JSON-RPC-interface.md passes false as the sixth positional argument descriptors. Since v30.0, legacy wallets can no longer be created, so the example fails as written:

$ bitcoin-cli -regtest createwallet mywallet false false "" false false true
error code: -4
error message:
descriptors argument must be set to "true"; it is no longer possible to create a legacy wallet.

This changes the argument to true in both the comment and the command. The example still shows positional arguments, including load_on_startup as the seventh, and with the change it creates the wallet without error. Tested with v31.1 on regtest.

No code or tests are affected, this is a documentation only change.

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External sites

• Code coverage & benchmarks: https://corecheck.dev/bitcoin/bitcoin/pulls/36460
• Ralph review <img src=https://review.fish.foo/assets/bitcoin/bitcoin/36460.png alt="Ralph review status"> https://git.fish.foo/bitcoin/bitcoin/pulls/36460#author-ralph

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ACK 58ff194754b368c6f601d426cccecb0dbbf98a3c

not sure why you invalidated the ACK by force pushing. Closing for now.

Also, This is an illustrative example of the schema and not something a user should copy-paste. It failing is probably a good thing.

Thanks for your interest in contributing! However, since there are hundreds of pending pull requests, I am closing this to focus review on the others. If you wish to contribute in the future, please focus on creating high-quality, original content that demonstrates a clear understanding of the project's requirements and goals. Also, see the contributing guidelines.

The force-push was to remove my email from the commit, though the ACK on 58ff194 keeps it linked anyway, so here I am. Sorry for resetting the ACK.

On the example: every other example in this doc runs without error, so this one should as well. Since v30.0 it fails as written, and setting descriptors to true still shows how positional and named arguments combine.

Going forward I'll help with review, since that's clearly where the bottleneck is.