[SPARK-3722][Docs]minor improvement and fix in docs

https://issues.apache.org/jira/browse/SPARK-3722

Author: WangTao <barneystinson@aliyun.com>

Closes #2579 from WangTaoTheTonic/docsWork and squashes the following commits:

6f91cec [WangTao] use more wording express
29d22fa [WangTao] delete the specified version link
34cb4ea [WangTao] Update running-on-yarn.md
4ee1a26 [WangTao] minor improvement and fix in docs
SPARK-4214. With dynamic allocation, avoid outstanding requests for more executors than pending tasks need.
Add tests and get num pending tasks from ExecutorAllocationListener
Whitespace fix
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