doc: update Java interop document (#5783)

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

Author: utamori

src/content/interop/java-interop.md

@@ -37,10 +37,8 @@ that uses `package:jnigen` to generate bindings for a simple class.
 
 - JDK
 - [Maven][]
-- (Optional) [`clang-format`][] to format the generated C bindings
 
 [Maven]: https://maven.apache.org/
-[`clang-format`]: https://clang.llvm.org/docs/ClangFormat.html
 
 ### Configure `jnigen`
 
@@ -56,9 +54,6 @@ This file contains the configuration for generating the bindings.
 
 ```yaml
 output:
-  c:
-    library_name: example
-    path: src/example/
   dart:
     path: lib/example.dart
     structure: single_file
@@ -69,7 +64,7 @@ classes:
   - 'dev.dart.Example'
 ```
 
-`path` specifies the path for the generated `c` and `dart` bindings.
+`path` specifies the path for the generated `dart` bindings.
 
 `source_path` specifies the path of the Java source file that
 you want to generate bindings for, 
@@ -90,7 +85,7 @@ public class Example {
 
 ### Generate the Dart bindings
 
-To generate the Dart (and C) bindings, run `jnigen` and
+To generate the Dart bindings, run `jnigen` and
 specify the config file using the `--config` option:
 
 ```console
@@ -120,11 +115,11 @@ print(Example.sum(a, b));
 ### Run the example
 
 Before running the example, 
-you must build the dynamic libraries for `jni` and the generated C files. 
+you must build the dynamic library for `jni`.
 The Java sources also must be compiled. To do so, run:
 
 ```console
-$ dart run jni:setup -p jni -s src/example
+$ dart run jni:setup
 $ javac java/dev/dart/Example.java
 ```