Update CODEOWNERS to keep only actual maintainers.

.github/CODEOWNERS

@@ -1,13 +1,9 @@
 # These owners will be the default owners for everything in the repo.
 # Unless a later match takes precedence, @global-owner1 and @global-owner2
 # will be requested for review when someone opens a pull request.
-*    @maxim-tschumak @netme @tkrop @ddufourboivin-zalando @zeitlinger
+*    @tkrop @zeitlinger @vadeg
 
 # Order is important; the last matching pattern takes the most precedence.
 # When someone opens a pull request that only modifies JS files, only @js-owner
 # and not the global owner(s) will be requested for a review.
 # *.js    @js-owner
-
-# You can also use email addresses if you prefer. They'll be used to look up
-# users just like we do for commit author emails.
-web-ui    @maxim-tschumak @tkrop @ddufourboivin-zalando @zeitlinger