feat: add Del func for requestHeader

[chaoranz758]

What type of PR is this?

feat

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• The description of this PR title is user-oriented and clear enough for others to understand.
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requestHeader 中添加 Del 函数，与 responseHeader 保持一致

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en: feat: add Del func for requestHeader
zh(optional): feat: requestHeader 中添加 Del 函数

(Optional) Which issue(s) this PR fixes:

(Optional) The PR that updates user documentation:

#946

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (d21a04a) 81.98% compared to head (1253389) 81.99%.

❗ Current head 1253389 differs from pull request most recent head ae1d003. Consider uploading reports for the commit ae1d003 to get more accurate results

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #950   +/-   ##
========================================
  Coverage    81.98%   81.99%           
========================================
  Files           97       97           
  Lines         9625     9628    +3     
========================================
+ Hits          7891     7894    +3     
  Misses        1260     1260           
  Partials       474      474           

Files Changed	Coverage Δ
pkg/protocol/header.go	78.15% <100.00%> (+0.07%)	⬆️

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[welkeyever]

LGTM, thx~