Fix a typo

Author: titsuki

doc/Language/typesystem.pod6

@@ -544,7 +544,7 @@ TODO
 
 =head3 Versioning and Authorship
 
-Versioning and authorship can be applied via adverbs X«C«:ver<>»|:ver<> (grammer)» and X«C«:auth<>»|:auth<> (grammer)».
+Versioning and authorship can be applied via adverbs X«C«:ver<>»|:ver<> (grammar)» and X«C«:auth<>»|:auth<> (grammar)».
 Both take a string as argument, for C<:ver> the string is converted to a
 L<Version|/type/Version> object. To query a grammars version and author use
 C<.^ver> and C<^.auth>.