rust-filepatterns: use literal b'#' instead of cast

rust-filepatterns: use literal b'#' instead of cast

--- a/rust/hg-core/src/filepatterns.rs	Sun Jul 21 12:46:57 2019 +0900
+++ b/rust/hg-core/src/filepatterns.rs	Sun Jul 21 13:00:54 2019 +0900
@@ -243,7 +243,7 @@
     for (line_number, mut line) in lines.split(|c| *c == b'\n').enumerate() {
         let line_number = line_number + 1;
 
-        if line.contains(&('#' as u8)) {
+        if line.contains(&b'#') {
             if let Some(cap) = comment_regex.captures(line) {
                 line = &line[..cap.get(1).unwrap().end()]
             }