Link PSR-7 errata via web to fix site deploy

Author: Jean85

accepted/PSR-7-http-message.md

@@ -75,7 +75,7 @@ referring to these interfaces.
 
 ### 1.2 HTTP Headers
 
-[cf. [errata](PSR-7-http-message-meta#71-validation-of-header-names-and-values)]
+[cf. [errata](https://www.php-fig.org/psr/psr-7/meta/#71-validation-of-header-names-and-values)]
 
 #### Case-insensitive header field names