chore(tooling): Drop Simon from code owner list

He isn't actively reviewing PR activity on anything and GitHub is being
increasinly grumpy about how I have to manually ignore the code owners
reviet requiremens. This isn't to cut Simon out of anything he wants to
be involved in, just to make PR workflows a littly easier to work with
by not needing admin overrides for everything.

.github/CODEOWNERS

@@ -1,5 +1,5 @@
 # Default
-*	@alerque @simoncozens
+*	@alerque
 
 # Language expertise
 languages/fr*	@sile-typesetter/lang-fr