Update flannel to v0.24.0 and remove multiclustercidr flag (#9075) #6979

Job	Run time
build / Build	6m 49s
Integration Tests (certrotation)	2m 8s
Integration Tests (etcdrestore)	2m 13s
Integration Tests (localstorage)	1m 55s
Integration Tests (startup)	7m 2s
Integration Tests (custometcdargs)	38s
Integration Tests (etcdsnapshot)	7m 37s
Integration Tests (kubeflags)	1m 8s
Integration Tests (longhorn)	2m 29s
Integration Tests (secretsencryption)	2m 13s
	34m 12s

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