Update docker.io/library/golang Docker tag to v1.26.3

Author: renovate[bot]

Dockerfile

@@ -1,5 +1,5 @@
 # Build the manager binary
-FROM docker.io/library/golang:1.23.6 as builder
+FROM docker.io/library/golang:1.26.3 as builder
 
 WORKDIR /workspace
 # Copy the Go Modules manifests