remove trailing whitespace

Author: coke

doc/Language/grammars.pod6

@@ -198,11 +198,11 @@ word boundary (C«<|w>»):
     # First <.ws> matches word boundary at the start of the line
     # and second <.ws> matches the whitespace between 'b' and 'c'
     say 'ab   c' ~~ /<.ws> ab <.ws> c /; # OUTPUT: «｢ab   c｣␤»
-    
+
     # Failed match: there is neither any whitespace nor a word
     # boundary between 'a' and 'b'
     say 'ab' ~~ /. <.ws> b/;             # OUTPUT: «Nil␤»
-    
+
     # Successful match: there is a word boundary between ')' and 'b'
     say ')b' ~~ /. <.ws> b/;             # OUTPUT: «｢)b｣␤»