Bump k8s version in envtest

... to the one consistent with the version in dependencies.

Author: kajinamit

Makefile

@@ -50,7 +50,7 @@ endif
 DEFAULT_IMG ?= quay.io/openstack-k8s-operators/mariadb-operator:latest
 IMG ?= $(DEFAULT_IMG)
 # ENVTEST_K8S_VERSION refers to the version of kubebuilder assets to be downloaded by envtest binary.
-ENVTEST_K8S_VERSION = 1.25.0
+ENVTEST_K8S_VERSION = 1.26
 
 # Get the currently used golang install path (in GOPATH/bin, unless GOBIN is set)
 ifeq (,$(shell go env GOBIN))