doc: update Java interop document

[utamori]

Pure Dart binding is now standard
This page needs to be updated so that newcomers are not confused

• Upgrade JNIGEN to v0.9.0
• Remove legacy C bindings

HosseinYousefi/jnigen_example#2

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[HosseinYousefi]

There are other mentions of the C bindings still available in the text. Please also change them.

[HosseinYousefi]

This can also be removed.

[utamori]

done

[HosseinYousefi]

I mentioned that there are other places where the C bindings are not removed.

However I cannot point you to them, as GitHub doesn't let me comment on unchanged lines.

It would be nice to allow changes, so we can commit to your fork.

So I'll try to review using links to the lines:

https://github.com/dart-lang/site-www/pull/5783/files#diff-ea7b67b16b35f54455c4e13a54b0e18a2645749b60ad4e960f94b288061e967fR88

-To generate the Dart (and C) bindings, run `jnigen` and
+To generate the Dart bindings, run `jnigen` and

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https://github.com/dart-lang/site-www/pull/5783/files#diff-ea7b67b16b35f54455c4e13a54b0e18a2645749b60ad4e960f94b288061e967fL123

-you must build the dynamic libraries for `jni` and the generated C files. 
+you must build the dynamic library for `jni`. 

[utamori]

@HosseinYousefi
I had missed it. Thanks for pointing that out.
If there's anything else, feel free to have it edited.

[HosseinYousefi]

LGTM! Thanks @utamori!