Update ui tests

Author: GuillaumeGomez

src/test/ui/parser/byte-literals.rs

@@ -8,5 +8,5 @@ pub fn main() {
     b'	';  //~ ERROR byte constant must be escaped
     b''';  //~ ERROR byte constant must be escaped
     b'é';  //~ ERROR byte constant must be ASCII
-    b'a  //~ ERROR unterminated byte constant
+    b'a  //~ ERROR unterminated byte constant [E0763]
 }

src/test/ui/parser/byte-literals.stderr

@@ -34,11 +34,12 @@ error: byte constant must be ASCII. Use a \xHH escape for a non-ASCII byte
 LL |     b'é';
    |       ^
 
-error: unterminated byte constant
+error[E0763]: unterminated byte constant
   --> $DIR/byte-literals.rs:11:6
    |
 LL |     b'a
    |      ^^^^
 
 error: aborting due to 7 previous errors
 
+For more information about this error, try `rustc --explain E0763`.