doc: make end comment consistent with start comment
@@ -133,7 +133,7 @@ Some productions are defined by exclusion of particular Unicode characters:
```{.ebnf .gram}
comment : block_comment | line_comment ;
-block_comment : "/*" block_comment_body * '*' + '/' ;
+block_comment : "/*" block_comment_body * "*/" ;
block_comment_body : [block_comment | character] * ;
line_comment : "//" non_eol * ;
```
