remove extra backtick

Author: gregsdennis

jsonschema-core.md

@@ -340,7 +340,7 @@ named schemas.
 Plain name fragments MUST follow XML's [NCName production](#xml-names), which
 allows for compatibility with the recommended plain name
 [syntax](#W3C.REC-xptr-framework-20030325) for XML-based media types.  For
-convenience, the `NCName`` syntax is reproduced here in ABNF form, using
+convenience, the `NCName` syntax is reproduced here in ABNF form, using
 a minimal set of rules: [^20]
 
 [^20] Note that the previous syntax for plain name fragment is a subset of this syntax, which used only the first line of each of the `NCNameStartChar`` and `NCNameChar`` rules.