[Release 1.27] Update flannel to v0.25.4 and fixed issue with IPv6 mask

[rbrtbnfgl]

Backport: #10422
Issue: #10425

[codecov]

Codecov Report

Attention: Patch coverage is 52.63158% with 18 lines in your changes missing coverage. Please review.

Project coverage is 36.11%. Comparing base (3ced503) to head (b17a155).

Files	Patch %	Lines
pkg/agent/flannel/flannel.go	52.63%	14 Missing and 4 partials ⚠️

❗ There is a different number of reports uploaded between BASE (3ced503) and HEAD (b17a155). Click for more details.

HEAD has 15 uploads less than BASE

Flag	BASE (3ced503)	HEAD (b17a155)
unittests	3	0
e2etests	18	6

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.27   #10429      +/-   ##
================================================
- Coverage         43.03%   36.11%   -6.93%     
================================================
  Files               163      160       -3     
  Lines             16534    13985    -2549     
================================================
- Hits               7115     5050    -2065     
+ Misses             8158     7940     -218     
+ Partials           1261      995     -266     

Flag	Coverage Δ
e2etests	36.11% <52.63%> (-10.14%)	⬇️
unittests	?

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