[Release 1.31] Update Flannel to v0.26.1

[rbrtbnfgl]

Backport for #7228

[mdrahman-suse]

Validated on release-1.31 with commit 5b9a8f8

$ rke2 -v
rke2 version v1.31.2+dev.5b9a8f82 (5b9a8f82e455d9e2da999c8e3f6b93174812175a)
go version go1.22.8 X:boringcrypto

$ kubectl get nodes -o yaml | grep 'hardened-flannel' -A1
      - docker.io/rancher/hardened-flannel@sha256:5e52b239c1407ba561fce06403d71aa177c3e54a96ae00430fef467ced586298
      - docker.io/rancher/hardened-flannel:v0.26.1-build20241107
      sizeBytes: 81056614
--
      - docker.io/rancher/hardened-flannel@sha256:5e52b239c1407ba561fce06403d71aa177c3e54a96ae00430fef467ced586298
      - docker.io/rancher/hardened-flannel:v0.26.1-build20241107
      sizeBytes: 81056614

$ sudo cat /var/lib/rancher/rke2/data/v1.31.2-dev.5b9a8f82-b14249a4a1c2/charts/rke2-flannel.yaml | grep rke2-flannel
  name: "rke2-flannel"
    helm.cattle.io/chart-url: "https://rke2-charts.rancher.io/assets/rke2-flannel/rke2-flannel-v0.26.100.tgz"

Windows

PS C:\Users\Administrator> C:\usr\local\bin\rke2.exe -v
rke2.exe version v1.31.2+dev.5b9a8f82 (5b9a8f82e455d9e2da999c8e3f6b93174812175a)
go version go1.22.8

PS C:\Users\Administrator> C:\var\lib\rancher\rke2\data\v1.31.2-dev.5b9a8f82-windows-amd64-8e2944fa2533\bin\flannel.exe -version
CNI Plugin flannel version v1.6.0-flannel1 (windows/amd64) commit 3389866d built on 2024-10-21T08:01:32Z
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

PS C:\Users\Administrator> C:\var\lib\rancher\rke2\data\v1.31.2-dev.5b9a8f82-windows-amd64-8e2944fa2533\bin\flanneld.exe -version
v0.26.1