Strategy#page_headers: Update for #curl_headers

`#curl_headers` was recently introduced into `Strategy#page_headers`
but only the call was modified and the method wasn't updated to
correctly work with the new return value, so all `HeaderMatch` checks
immediately started failing with an error.

This commit includes changes that return `#page_headers` to a working
state. I've removed the `result.assert_success!` call because it
prevents a few checks from being retried with `GET` (`firefox-cn`,
`krisp`, `prepros`).

Library/Homebrew/livecheck/strategy.rb

@@ -182,16 +182,15 @@ module Homebrew
         headers = []
 
         [:default, :browser].each do |user_agent|
-          output, _, status = curl_headers(
+          parsed_output = curl_headers(
             url,
             wanted_headers:    ["location", "content-disposition"],
             use_homebrew_curl: homebrew_curl,
             user_agent:        user_agent,
             **DEFAULT_CURL_OPTIONS,
           )
-          next unless status.success?
+          next if parsed_output.blank?
 
-          parsed_output = parse_curl_output(output, max_iterations: MAX_PARSE_ITERATIONS)
           parsed_output[:responses].each { |response| headers << response[:headers] }
           break if headers.present?
         end

Library/Homebrew/utils/curl.rb

@@ -213,7 +213,8 @@ module Utils
         )
 
         # 22 means a non-successful HTTP status code, not a `curl` error, so we still got some headers.
-        if result.success? || result.exit_status == 22
+        next if !result.success? && result.exit_status != 22
+
         parsed_output = parse_curl_output(result.stdout)
 
         # If we didn't get any wanted header yet, retry using `GET`.
@@ -223,8 +224,7 @@ module Utils
         return parsed_output if result.success?
       end
 
-        result.assert_success!
-      end
+      nil
     end
 
     # Check if a URL is protected by CloudFlare (e.g. badlion.net and jaxx.io).