Fix $LOAD_PATH to correctly require files

Other I would get errors like:

LoadError: cannot load such file -- rails/api/generator (LoadError)

We were loading the installed rails gem and not the current subdirectories

This can be reproduced by doing `bundle clean --force` then `rake`

Fixes rails#50739

Rakefile

@@ -2,7 +2,9 @@
 
 require "net/http"
 
-$:.unshift __dir__
+$LOAD_PATH.unshift __dir__
+$LOAD_PATH.unshift(*Dir.glob(File.join(__dir__, "*", "lib")))
+
 require "tasks/release"
 require "railties/lib/rails/api/task"