go.mod: bump to Go 1.19

Go 1.20 will be there soon, I think it's time to move our go.mod to
latest stable. We can then remove the compat in our vendor.Dockerfile

Downstream projects like compose or github.com/linuxkit/linuxkit should
not be affected.

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

hack/dockerfiles/vendor.Dockerfile

@@ -13,7 +13,7 @@ RUN --mount=target=/context \
   --mount=target=/go/pkg/mod,type=cache <<EOT
 set -e
 rsync -a /context/. .
-go mod tidy -compat=1.17
+go mod tidy
 go mod vendor
 mkdir /out
 cp -r go.mod go.sum vendor /out