Update Hebrew language code to he per IANA registry (openai#401)

* Update Hebrew language code to he per IANA registry

Per [IANA registry](https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry), `iw` was deprecated as the code for Hebrew in 1989 and the preferred code is `he`

The correct subtag: 
```
%%
Type: language
Subtag: he
Description: Hebrew
Added: 2005-10-16
Suppress-Script: Hebr
%%
``` 
And the deprecation
```
%%
Type: language
Subtag: iw
Description: Hebrew
Added: 2005-10-16
Deprecated: 1989-01-01
Preferred-Value: he
Suppress-Script: Hebr
%%
```

* Update hebrew ISO code to he

Per discussion, it's ok to make this change without backwards compatibility

whisper/tokenizer.py

@@ -28,7 +28,7 @@
  "hi": "hindi",
  "fi": "finnish",
  "vi": "vietnamese",
- "iw": "hebrew",
+ "he": "hebrew",
  "uk": "ukrainian",
  "el": "greek",
  "ms": "malay",