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### What changes were proposed in this pull request?
As Title
### Why are the changes needed?
Since 0.3.1, Celeborn changed the default value of `celeborn.worker.directMemoryRatioToResume` from `0.5` to `0.7`.
the doc should be update
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
PASS GA
Closes#1931 from jiaoqingbo/ratiofix.
Authored-by: jiaoqingbo <1178404354@qq.com>
Signed-off-by: zky.zhoukeyong <zky.zhoukeyong@alibaba-inc.com>
f1713dacaf