Fix uninitialized constant error in GitHub.open

The error handling depends on side effects of `require "net/https"`,
so it should be wrapped in an explicit begin block.

cf. Homebrew/homebrew#30407.

Library/Homebrew/utils.rb

@@ -311,6 +311,8 @@ module GitHub extend self
     }
 
     default_headers['Authorization'] = "token #{HOMEBREW_GITHUB_API_TOKEN}" if HOMEBREW_GITHUB_API_TOKEN
+
+    begin
       Kernel.open(url, default_headers.merge(headers)) do |f|
         yield Utils::JSON.load(f.read)
       end
@@ -321,6 +323,7 @@ module GitHub extend self
     rescue Utils::JSON::Error => e
       raise Error, "Failed to parse JSON response\n#{e.message}", e.backtrace
     end
+  end
 
   def handle_api_error(e)
     if e.io.meta["x-ratelimit-remaining"].to_i <= 0