Update Go version to 1.26.3

See the release history: https://go.dev/doc/devel/release#go1.26.3.

Author: arnested

go.mod

@@ -1,6 +1,6 @@
 module arnested.dk/go/healthy
 
-go 1.26.2
+go 1.26.3
 
 require github.com/docker/docker v28.5.2+incompatible