chore: update code owners (#23357)

And then there was 1.

Author: just-mitch

CODEOWNERS

@@ -29,7 +29,7 @@
 /playground/vite.config.ts @Thunkar
 
 # Notify turtles of changes to L1-contracts
-/l1-contracts/src @LHerskind @Maddiaa0 @just-mitch
+/l1-contracts/src @just-mitch
 
 # Notify the circuit team of changes to the protocol circuits
 /noir-projects/noir-protocol-circuits @LeilaWang