*: update gin to v1.9.1 for security reason

[mornyx]

Refs:

• Update module github.com/gin-gonic/gin to v1.9.1 [SECURITY] - autoclosed xiabee/tidb-dashboard-security-test#11

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release@7cb8b7f). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff            @@
##             release   #1615   +/-   ##
=========================================
  Coverage           ?   9.23%           
=========================================
  Files              ?     123           
  Lines              ?   13007           
  Branches           ?       0           
=========================================
  Hits               ?    1201           
  Misses             ?   11675           
  Partials           ?     131           

Flag	Coverage Δ
backend_integration	9.23% <0.00%> (?)

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