[Release-1.30] - Bump flannel to v0.26.7

[brandond]

Backport fix for Bump flannel to v0.26.7

• Bump flannel to v0.26.7 #12152

[VestigeJ]

🟢 clear;k3s -v; sudo /var/lib/rancher/k3s/data/cni/flannel --version

k3s version v1.30.11+k3s-925934a2 (925934a2)
go version go1.23.6
CNI Plugin flannel version v1.6.0-flannel1+v0.26.7 (linux/amd64) commit HEAD built on 2025-04-18T18:01:38Z
CNI protocol versions supported: 0.1.0, 0.2.0, 0.3.0, 0.3.1, 0.4.0, 1.0.0, 1.1.0