DEV: Change use of Redis flushall to flushdb.

FLUSHALL removes all keys from all databases. Instead we only want to
remove keys from the current Redis database.

spec/services/word_watcher_spec.rb

@@ -7,7 +7,7 @@ describe WordWatcher do
   let(:raw) { "Do you like liquorice?\n\nI really like them. One could even say that I am *addicted* to liquorice. Anf if\nyou can mix it up with some anise, then I'm in heaven ;)" }
 
   after do
-    Discourse.redis.flushall
+    Discourse.redis.flushdb
   end
 
   describe '.word_matcher_regexp' do