Enable the namespaced keysets for consistency in the final test

Although they aren't mentioned here explicitly, it's probably a good
idea nevertheless for consistency with legacy pact tests' behaviour.

pact-core-tests/pact-tests/namespaces.repl

@@ -278,7 +278,7 @@
 
 (begin-tx)
 
-(env-exec-config [])
+(env-exec-config ['RequireKeysetNs])
 
 (expect
   "Setting namespace back to root namespace post-Pact 4.7 fork succeeds"