Simplify `as` passed check.

`if !var.nil?` is the same as just `if var`

actionpack/lib/action_dispatch/testing/integration.rb

@@ -336,7 +336,7 @@ def process(method, path, params: nil, headers: nil, env: nil, xhr: false, as: n
             end
             path = request_encoder.append_format_to location.path
             path = location.query ? "#{path}?#{location.query}" : path
-          elsif !as.nil?
+          elsif as
             location = URI.parse(path)
             path = request_encoder.append_format_to location.path
             path = location.query ? "#{path}?#{location.query}" : path