Update URL

docs/manual/external-checkers.tex

@@ -119,7 +119,7 @@
 checker that provides even more safety:  it ensures that you don't
 use SQL features that are not supported by your database
 implementation.  You can learn about the SQL checker at
-\url{https://blog.jooq.org/2016/05/09/jsr-308-and-the-checker-framework-add-even-more-typesafety-to-jooq-3-9/}.
+\url{https://blog.jooq.org/jsr-308-and-the-checker-framework-add-even-more-typesafety-to-jooq-3-9/}.
 
 
 \sectionAndLabel{Read Checker for CERT FIO08-J}{read-checker}