Add missing "controller-tools" update instructions to the v1.25.0 mig…

…ration guide (#6525)

Signed-off-by: Timo Walter <twalter@walter-se.com>

website/content/en/docs/upgrading-sdk-version/v1.25.0.md

@@ -33,6 +33,7 @@ weight: 998975000
         - docker buildx rm project-v3-builder
         rm Dockerfile.cross
     ```
+
 3. (go/v3) Bump dependencies in go.mod file
 
     ```go
@@ -47,6 +48,10 @@ weight: 998975000
         sigs.k8s.io/controller-runtime v0.13.0
     ```
 
+4. (go/v3) Update `controller-tools` from `0.9.2` to `0.10.0`. 
+
+   In the `Makefile` file, replace `CONTROLLER_TOOLS_VERSION ?= v0.9.2` with `CONTROLLER_TOOLS_VERSION ?= v0.10.0`
+
 _See [#6047](https://github.com/operator-framework/operator-sdk/pull/6047) for more details._
 
 ## For multi-arch build support, add docker-buildx target to project Makefile