dep: update tailwindcss to v4.0.0-beta.4

https://github.com/tailwindlabs/tailwindcss/releases/tag/v4.0.0-beta.4

Author: flavorjones

lib/tailwindcss/ruby/upstream.rb

@@ -1,7 +1,7 @@
 module Tailwindcss
   module Ruby
     module Upstream
-      VERSION = "v4.0.0-beta.3"
+      VERSION = "v4.0.0-beta.4"
 
       # rubygems platform name => upstream release filename
       NATIVE_PLATFORMS = {