Simplify docker.#Run

* `cmd` is renamed to `command` for readability
  * `script` is removed. Feature moves up the stack (bash.#Run,
    python.#Run)

Signed-off-by: Solomon Hykes <solomon@dagger.io>

pkg/universe.dagger.io/alpine/alpine.cue

@@ -27,7 +27,7 @@ import (
 			},
 			for pkgName, pkg in packages {
 				docker.#Run & {
-					cmd: {
+					command: {
 						name: "apk"
 						args: ["add", "\(pkgName)\(pkg.version)"]
 						flags: {