Dockerfile: Bump Go version to 1.22

go1.23 is now available making go1.22 the oldest supported release. We
should now update the Dockerfile accordingly to make go-version-check.sh
happy.

Signed-off-by: Anoop C S <anoopcs@samba.org>

Dockerfile

@@ -1,5 +1,5 @@
 # Build the manager binary
-FROM docker.io/golang:1.21 as builder
+FROM docker.io/golang:1.22 as builder
 ARG GIT_VERSION="(unset)"
 ARG COMMIT_ID="(unset)"
 ARG ARCH=""