CLIENT-SPECIFICATION: switch to https and remove `www.` (#13910)

CLIENT-SPECIFICATION.md

@@ -42,7 +42,7 @@ Option             | Required?   | Meaning
 
 Clients MUST implement both the short and long versions of an option.
 
-Additional decoration MAY be printed if the standard output is a [TTY](http://www.linusakesson.net/programming/tty/index.php). If not, then the output MUST not contain any additional decorations. For example, a page list MUST be formatted with one page name per line (to enable easy manipulation using standard CLI tools such as `grep` etc.).
+Additional decoration MAY be printed if the standard output is a [TTY](https://linusakesson.net/programming/tty/index.php). If not, then the output MUST not contain any additional decorations. For example, a page list MUST be formatted with one page name per line (to enable easy manipulation using standard CLI tools such as `grep` etc.).
 
 Clients MAY support additional custom arguments and syntax not documented here.