Remove tabs from grammar doc

doc/Language/grammars.pod6

@@ -439,16 +439,16 @@ Once the arguments are passed in, they can be used in a call to a named regex in
 =begin code
     grammar demonstrate-arguments-again
         rule TOP ($word) {
-	   <phrase-stem><added-word($word)>
+        <phrase-stem><added-word($word)>
         }
 
         rule phrase-stem {
-	   "I like"
-	}
+           "I like"
+        }
 
         rule added-word($passed-word) {
            $passed-word
-	}
+        }
      }
 
      say demonstrate-arguments-again.parse("I like vegetables", :args(("vegetables",)));
@@ -463,13 +463,13 @@ Alternatively, you can initialise dynamic variables and use any arguments that w
      grammar demonstrate-arguments-dynamic {
          rule TOP ($*word, $*extra) {
             <phrase-stem><added-words>
-	  }
+         }
          rule phrase-stem {
-	    "I like"
-	 }
+            "I like"
+         }
          rule added-words {
-	    $*word $*extra
-	 }
+            $*word $*extra
+         }
       }
 
      say demonstrate-arguments-dynamic.parse("I like everything else", :args(("everything", "else")));