chore: update PULL_REQUEST_TEMPLATE.md

[Radeity]

Purpose of the PR

• Synchronized update, refer to https://github.com/apache/incubator-hugegraph/pull/2234

Main Changes

Verifying these changes

• [x] Trivial rework / code cleanup without any test coverage. (No Need)
• [ ] Already covered by existing tests, such as (please modify tests here).
• [ ] Need tests and can be verified as follows:

Does this PR potentially affect the following parts?

• [x] Nope
• [ ] Dependencies (add/update license info)
• [ ] Modify configurations
• [ ] The public API
• [ ] Other affects (typed here)

Documentation Status

• [ ] Doc - TODO
• [ ] Doc - Done
• [x] Doc - No Need

[codecov[bot]]

Codecov Report

Merging #257 (90e556c) into master (024d1aa) will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #257   +/-   ##
=========================================
  Coverage     85.86%   85.86%           
  Complexity     3235     3235           
=========================================
  Files           344      344           
  Lines         12115    12115           
  Branches       1092     1092           
=========================================
  Hits          10402    10402           
  Misses         1190     1190           
  Partials        523      523           

see 1 file with indirect coverage changes

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