### _Why are the changes needed?_
As issue [RANGER-4672](https://github.com/apache/kyuubi/issues/4672) reported unresovled failures on Ranger 0.6.0, update docs for unsupported Ranger version 0.6.0.
### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible
- [ ] Add screenshots for manual tests if appropriate
- [ ] [Run test](https://kyuubi.readthedocs.io/en/master/develop_tools/testing.html#running-tests) locally before make a pull request
Closes#4673 from bowenliang123/drop-ranger-0.6.0.
Closes#4672
5049596c0 [liangbowen] update README.md
f9ea53449 [liangbowen] drop support for Ranger 0.6.0
Authored-by: liangbowen <liangbowen@gf.com.cn>
Signed-off-by: liangbowen <liangbowen@gf.com.cn>
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