image: use golang builder 1.21

Align Go version with other samba repositories.

Signed-off-by: Shachar Sharon <[email protected]>

Author: synarete

Dockerfile

@@ -1,5 +1,5 @@
 # Build smbmetrics
-FROM docker.io/golang:1.18 as builder
+FROM docker.io/golang:1.21 as builder
 ARG GIT_VERSION="(unset)"
 ARG COMMIT_ID="(unset)"
 ARG ARCH=""