jsonschema: add missing colon to link block

Without this, not only is the one link not valid, the entire section is
considered invalid and none of the link references are used.

Author: prattmic

jsonschema/doc.go

@@ -95,7 +95,7 @@ are recorded in the schema, but ignored during validation.
 [section 7 of the validation spec]: https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-validation-00#rfc.section.7
 [section 8 of the validation spec]: https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-validation-00#rfc.section.8
 [learnjsonschema.org]: https://www.learnjsonschema.com/2020-12/format-annotation/format/
-[this table of differences] https://github.com/dlclark/regexp2?tab=readme-ov-file#compare-regexp-and-regexp2
+[this table of differences]: https://github.com/dlclark/regexp2?tab=readme-ov-file#compare-regexp-and-regexp2
 [annotations]: https://json-schema.org/draft/2020-12/json-schema-core#name-annotations
 */
 package jsonschema