[Release 1.29] Update flannel to v0.25.4 and fixed issue with IPv6 mask

[rbrtbnfgl]

Backport: #10422
Issue: #10424

[codecov]

Codecov Report

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

Project coverage is 43.58%. Comparing base (83ae095) to head (09ac731).

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 (83ae095) and HEAD (09ac731). Click for more details.

HEAD has 33 uploads less than BASE

Flag	BASE (83ae095)	HEAD (09ac731)
unittests	3	1
inttests	30	10
e2etests	17	6

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.29   #10427      +/-   ##
================================================
- Coverage         49.91%   43.58%   -6.34%     
================================================
  Files               163      163              
  Lines             14205    14233      +28     
================================================
- Hits               7091     6204     -887     
- Misses             5769     6846    +1077     
+ Partials           1345     1183     -162     

Flag	Coverage Δ
e2etests	36.59% <52.63%> (-9.91%)	⬇️
inttests	37.08% <44.73%> (-0.01%)	⬇️
unittests	16.38% <0.00%> (-0.05%)	⬇️

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