[Improvement] Improve docs for relasing 0.7.0

[zhoujinsong]

Why are the changes needed?

Fix some issues of docs for releasing 0.7.0

Brief change log

• Fix some doc issues

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

• [x] Run test locally before making a pull request

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable )

[zhoujinsong]

I have made some changes due to the review suggestion, PTAL. @tcodehuber @baiyangtx