utils/github: fix reverted order of credentials

We always return the token/password first and, if applicable, the user
name is the second element in the returned array.

Closes Homebrew#581.

Signed-off-by: Martin Afanasjew <martin@afanasjew.de>

Library/Homebrew/utils/github.rb

@@ -50,7 +50,7 @@ def api_credentials
       if ENV["HOMEBREW_GITHUB_API_TOKEN"]
         ENV["HOMEBREW_GITHUB_API_TOKEN"]
       elsif ENV["HOMEBREW_GITHUB_API_USERNAME"] && ENV["HOMEBREW_GITHUB_API_PASSWORD"]
-        [ENV["HOMEBREW_GITHUB_API_USERNAME"], ENV["HOMEBREW_GITHUB_API_PASSWORD"]]
+        [ENV["HOMEBREW_GITHUB_API_PASSWORD"], ENV["HOMEBREW_GITHUB_API_USERNAME"]]
       else
         github_credentials = api_credentials_from_keychain
         github_username = github_credentials[/username=(.+)/, 1]