docs: typo in routing.md, wrappers users => user

[swaghua]

Checklist

• npm test passes
• tests are included
• documentation is changed or added
• commit message follows commit guidelines

Description of change

• any feature?
• close https://github.com/umijs/umi/ISSUE_URL

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View rendered docs/docs/routing.zh-CN.md

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[codecov]

Codecov Report

Merging #4110 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4110   +/-   ##
=======================================
  Coverage   83.99%   83.99%           
=======================================
  Files         129      129           
  Lines        2549     2549           
  Branches      642      642           
=======================================
  Hits         2141     2141           
  Misses        400      400           
  Partials        8        8

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