Removing a couple of 404s

Mainly related to #561

doc/Language/regexes.pod6

@@ -146,7 +146,7 @@ can be matched with C<\v>, and C<\s> matches any kind of whitespace.
 
 C<\n> matches a single, logical newline character.
 What is considered as a I<single newline character> is defined via the compile time
-variable L<$?NL>, and the L<newline pragma|/language/pragmas>.
+variable L<$?NL|/language/variables##index-entry-%24%3FNL>, and the L<newline pragma|/language/pragmas>.
 Therefore C<\n> is supposed to be able to either match a Unix-like newline "\n"
 or a Microsoft Windows style one "\r\n".
 

doc/Type/Num.pod6

@@ -39,7 +39,7 @@ to represent:
     say atan ∞;          # OUTPUT: «1.5707963267949␤»
     say -∞ < 42 < ∞;     # OUTPUT: «True␤»
 
-Division of an infinity by an infinity results in a L<NaN>:
+Division of an infinity by an infinity results in a C<NaN>:
 
     say ∞/∞;             # OUTPUT: «NaN␤»
 

htmlify.p6

@@ -5,15 +5,15 @@ use v6;
 
 This script isn't in bin/ because it's not meant to be installed.
 For syntax highlighting, needs node.js installed.
-Please run make init-highlights to automatically pull in the highlighting
+Please run C<make init-highlights> to automatically pull in the highlighting
 grammar and build the highlighter.
 
 For doc.perl6.org, the build process goes like this:
 a cron job on hack.p6c.org as user 'doc.perl6.org' triggers the rebuild.
 
     */5 * * * * flock -n ~/update.lock -c ./doc/util/update-and-sync > update.log 2>&1
 
-util/update-and-sync is under version control in the perl6/doc repo (same as
+C<util/update-and-sync> is under version control in the perl6/doc repo (same as
 this file), and it first updates the git repository. If something changed, it
 runs htmlify, captures the output, and on success, syncs both the generated
 files and the logs. In case of failure, only the logs are synchronized.