[Release 1.28] Update flannel to v0.25.4 and fixed issue with IPv6 mask

[rbrtbnfgl]

Backport: #10422
Issue: #10426

[codecov]

Codecov Report

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

Project coverage is 36.37%. Comparing base (617b0e8) to head (cc14321).

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 (617b0e8) and HEAD (cc14321). Click for more details.

HEAD has 16 uploads less than BASE

Flag	BASE (617b0e8)	HEAD (cc14321)
unittests	3	0
e2etests	19	6

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.28   #10428      +/-   ##
================================================
- Coverage         42.82%   36.37%   -6.45%     
================================================
  Files               163      160       -3     
  Lines             16637    14080    -2557     
================================================
- Hits               7125     5122    -2003     
+ Misses             8255     7959     -296     
+ Partials           1257      999     -258     

Flag	Coverage Δ
e2etests	36.37% <52.63%> (-9.67%)	⬇️
unittests	?

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