Merge pull request #22299 from claudiob/fix-doc-tt

[ci skip] Fix <tt> in doc around +maximum(:updated_at)

actionpack/lib/action_controller/metal/conditional_get.rb

@@ -66,7 +66,7 @@ def etag(&etagger)
     #
     # You can also pass an object that responds to +maximum+, such as a
     # collection of active records. In this case +last_modified+ will be set by
-    # calling +maximum(:updated_at)+ on the collection (the timestamp of the
+    # calling <tt>maximum(:updated_at)</tt> on the collection (the timestamp of the
     # most recently updated record) and the +etag+ by passing the object itself.
     #
     #   def index