Provide better link when rate limit exceeded error is thrown

Closes Homebrew/homebrew#45134.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Library/Homebrew/manpages/brew.1.md

@@ -636,6 +636,8 @@ can take several different forms:
     <https://developer.github.com/v3/#rate-limiting> for more information.
     Homebrew uses the GitHub API for features such as `brew search`.
 
+    *NOTE*: Homebrew doesn't require permissions for any of the scopes.
+
   * HOMEBREW\_LOGS:
     If set, Homebrew will use the given directory to store log files.
 

Library/Homebrew/utils.rb

@@ -419,8 +419,8 @@ module GitHub
     def initialize(reset, error)
       super <<-EOS.undent
         GitHub #{error}
-        Try again in #{pretty_ratelimit_reset(reset)}, or create an personal access token:
-          https://github.com/settings/tokens
+        Try again in #{pretty_ratelimit_reset(reset)}, or create a personal access token:
+          https://github.com/settings/tokens/new?scopes=&description=Homebrew
         and then set the token as: HOMEBREW_GITHUB_API_TOKEN
       EOS
     end