FIX: ruby bench script no longer working

The library used to generate random text changed, this caused the title
of the topic used for testing to change, which meant the slug changed, so
a hit to the topic was a redirect

This fix gives the topic used for performance testing a static name to avoid
this issue in future

script/bench.rb

@@ -231,7 +231,7 @@ begin
   tests = [
     ["categories", "/categories"],
     ["home", "/"],
-    ["topic", "/t/oh-how-i-wish-i-could-shut-up-like-a-tunnel-for-so/179"]
+    ["topic", "/t/i-am-a-topic-used-for-perf-tests/179"]
     # ["user", "/u/admin1/activity"],
   ]