Fix typo.

Author: flexibeast

doc/Language/grammars.pod6

@@ -214,7 +214,7 @@ token, it can be used to trigger an Action class method. In the following
 grammar we look for Arabic digits and define a C<succ> token with the always
 succeed assertion.
 
-In the action class, we use calles to the C<succ> method to do set up (in this
+In the action class, we use calls to the C<succ> method to do set up (in this
 case, we prepare a new element in C<@!numbers>). In the C<digit> method,
 we convert an Arabic digit into a Devanagari digit and add it to the last
 element of C<@!numbers>. Thanks to C<succ>, the last element will always be