Remove xfail-pretty directives from working tests

Author: brson

src/test/run-pass/interior-vec.rs

@@ -1,5 +1,3 @@
-// xfail-pretty
-
 import rusti::ivec_len;
 
 native "rust-intrinsic" mod rusti {

src/test/run-pass/macro-by-example-2.rs

@@ -1,5 +1,3 @@
-// xfail-pretty
-
 fn main() {
     #macro([#zip_or_unzip[[x, ...], [y, ...]], [[x, y], ...]],
            [#zip_or_unzip[[xx, yy], ...], [[xx, ...], [yy, ...]]]);