fix GitHub notification interface return "Unable to parse If-Modified…

[AsherSu]

…-Since request header"

Description

fix GitHub notification interface return "Unable to parse If-Modified-Since request header" (fix #1985)

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 83.07%. Comparing base (e4ef482) to head (11c65f4).

Files with missing lines	Patch %	Lines
.../java/org/kohsuke/github/GHNotificationStream.java	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1984      +/-   ##
============================================
- Coverage     83.10%   83.07%   -0.03%     
  Complexity     2331     2331              
============================================
  Files           231      231              
  Lines          7172     7173       +1     
  Branches        378      379       +1     
============================================
- Hits           5960     5959       -1     
- Misses          974      975       +1     
- Partials        238      239       +1     

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