Resolves LH #6063, should be :expires_in not :expire_in

activesupport/lib/active_support/cache.rb

@@ -210,8 +210,8 @@ def self.instrument
       # be specified as an option to the construction in which call all entries will be
       # affected. Or it can be supplied to the +fetch+ or +write+ method for just one entry.
       #
-      #   cache = ActiveSupport::Cache::MemoryStore.new(:expire_in => 5.minutes)
-      #   cache.write(key, value, :expire_in => 1.minute)  # Set a lower value for one entry
+      #   cache = ActiveSupport::Cache::MemoryStore.new(:expires_in => 5.minutes)
+      #   cache.write(key, value, :expires_in => 1.minute)  # Set a lower value for one entry
       #
       # Setting <tt>:race_condition_ttl</tt> is very useful in situations where a cache entry
       # is used very frequently unver heavy load. If a cache expires and due to heavy load