Make launch command require only 40% plane efficiency

This is to make it consistent with automatic missile launch.

info/launch.t

@@ -37,7 +37,7 @@ Once a satellite has been launched, it can not be moved again.
 .s1
 Note here that it is much safer to use 100% missiles than those which
 are less efficient,
-and missiles below 60% cannot be launched.
+and missiles below 40% cannot be launched.
 .s1
 The formula for the chance that a missile hits its target is in
 \*Qinfo Hitchance\*U.

src/lib/commands/laun.c

@@ -93,7 +93,7 @@ laun(void)
 	    }
 	}
 
-	if (plane.pln_effic < 60) {
+	if (plane.pln_effic < 40) { 
 	    pr("%s is damaged (%d%%)\n", prplane(&plane), plane.pln_effic);
 	    continue;
 	}