misc: relax go.mod version (#183)

Go isn't quite clear on what it wants the `go` directive to be in
`go.mod`, but the community consensus is to use the `.0` patch release
of the oldest supported Go version. Granted, that's generally the advice
for libraries but there's no harn in relaxing this version for this
module that's going to be built as a container image.

Author: sudomateo

go.mod

@@ -1,6 +1,6 @@
 module github.com/oxidecomputer/oxide-cloud-controller-manager
 
-go 1.25.3
+go 1.25.0
 
 require (
 	github.com/google/uuid v1.6.0