build: Set go version to 1.23 in go.mod

Hopefully we can do without the toolchain directive, and `go 1.23` will
be enough, and we won't need to change it `go 1.23.0`.
The latter is not great together with the way we use actions/setup-go,
it would always build with 1.23.0 instead of the latest minor release.
```
        uses: actions/setup-go@v5
        with:
          go-version: ${{ matrix.go }}
```

Author: cfergeau

go.mod

@@ -1,8 +1,6 @@
 module github.com/crc-org/macadam
 
-go 1.22.6
-
-toolchain go1.23.2
+go 1.23
 
 require (
 	github.com/containers/common v0.61.1-0.20241125172552-a801fac4edc0