fix .style.yapf
fix .style.yapf

This is for error like
```
...
  File "/usr/local/google/home/tikuta/.vpython-root/f5511b/lib/python2.7/site-packages/yapf/yapflib/style.py", line 798, in _CreateStyleFromConfigParser
    base_style = _STYLE_NAME_TO_FACTORY[based_on]()
KeyError: 'chromium'
```

I copied this from
https://source.chromium.org/chromium/chromium/tools/depot_tools/+/main:.style.yapf

Change-Id: I3141931db8ab033abaffdc671c29feed52d3b242
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/3246772
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
Commit-Queue: Fumitoshi Ukai <0e88e065dd7f7d7f11da28b068df91c65342563c@google.com>
Reviewed-by: Fumitoshi Ukai <0e88e065dd7f7d7f11da28b068df91c65342563c@google.com>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py