docs(downlaod)：update the docs of download(#1453)

[Nliver]

Summary about this PR

Issue Number: close #1453

Tests Check List

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Changelog

• New Feature
• Bug Fix
• Performance Improvement
• Build/Testing/CI/CD
• Documentation
• Not for changelog (changelog entry is not required)

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features

[mergify]

This pull request's title should follow requirements next. @Nliver please check it 👇.

Valid format:

fix(vc): fix sth..... (#3306)
  ^         ^---------^  ^----^
  |         |            |
  |         +            +-> you issue id.
  |         |
  |         +-> Summary in present tense.
  |
  +-------> Type: feat, fix, docs, workflow, style, refactor, test, website, chore

Valid types:

• feat: new feature for stonedb
• fix: bug fix for stonedb
• docs: changes to the documentation
• workflow: ci/cd in .github
• perf: Changes to improve code performance
• refactor: refactoring production code, eg. renaming a variable
• style: formatting, missing semi colons, etc; no production code change
• test: adding missing tests, refactoring tests; no production code change
• website
• chore: updating grunt tasks etc; no production code change

[mergify]

Thanks for the contribution!
I have applied any labels matching special text in your PR Changelog.

Please review the labels and make any necessary changes.

[hustjieke]

LGTM