Remove no longer usable investments rake task

lib/tasks/investments.rake

@@ -1,12 +0,0 @@
-namespace :investments do
-  namespace :internal_comments do
-    desc "Migrate internal_comments textarea to a first comment on internal thread"
-    task migrate_to_thread: :environment do
-      comments_author_id = Administrator.first.user.id
-      Budget::Investment.where.not(internal_comments: [nil, '']).find_each do |investment|
-        Comment.create(commentable: investment, user_id: comments_author_id,
-                       body: investment.internal_comments, valuation: true)
-      end
-    end
-  end
-end