linux: Ignore "--yes" for rpm-ostree upgrade (#849)

Previously when performing the "system" upgrade step, rpm-ostree would
be passed a "--yes" argument when it was configured in topgrade.
However, this is not an option available for rpm-ostree, so it would
cause an error and abort execution of the updates.

src/steps/os/linux.rs

@@ -164,10 +164,6 @@ fn upgrade_redhat(ctx: &ExecutionContext) -> Result<()> {
         if ctx.config().rpm_ostree() {
             let mut command = ctx.run_type().execute(ostree);
             command.arg("upgrade");
-            if ctx.config().yes(Step::System) {
-                command.arg("-y");
-            }
-
             return command.check_run();
         }
     };