Fixed mixed tabs and spaces in one of the code examples

Perhaps we should replace all tabs with spaces? This will eliminate all such
occurances of mixed indentation styles.

Author: AlexDaniel

doc/Language/subscripts.pod

@@ -308,7 +308,7 @@ Dimensions in subscripts are separated by a semiconon, allowing to mix lists of
 elements and dimensions.
 
     my @twodim = (<a b c>, (1,2,3));
-	dd @twodim;
+    dd @twodim;
     # OUTPUT«Array @twodim = [("a", "b", "c"), (1, 2, 3)]␤»
     dd @twodim[0,1;1]; # 2nd element of both lists
     # OUTPUT«("b", 2)␤»