UI: Corrected ns.tail examples to ns.ui.openTail (#2270)

Changed to ns.ui.openTail in the example text where needed.

markdown/bitburner.ns.printf.md

@@ -43,6 +43,6 @@ ns.printf("My age in binary is %b.", age);
 ns.printf("My age in scientific notation is %e.", age);
 ns.printf("In %d seconds, I'll be %s.", 6, "Byte");
 ns.printf("Am I a nibble? %t", (4 === age));
-ns.tail();
+ns.ui.openTail();
 ```