Fix typo

Author: lizmat

doc/Type/Str.pod6

@@ -315,7 +315,7 @@ around character names is ignored.
 
 Note that unlike C<\c[...]> construct available in string interpolation,
 C<uniparse> does not accept decimal numerical values. Use L<chr> routine to
-covert those:
+convert those:
 
     say "\c[1337]"; # OUTPUT: «Թ␤»
     say '1337'.chr; # OUTPUT: «Թ␤»