Remove unused budget attributes

Tags and help links can be edited, but aren't used anywhere. Since we
don't know what the intended behavior was, I'm removing them for now.

My best guess is tags were supposed to be used so investments for a
budget can only be assigned tags present in the budget. Achieving that
behavior wouldn't be a trivial task.

db/migrate/20191031210734_remove_help_link_from_budgets.rb

@@ -0,0 +1,6 @@
+class RemoveHelpLinkFromBudgets < ActiveRecord::Migration[5.0]
+  def change
+    remove_column :budgets, :help_link, :string
+    remove_column :tags, :budgets_count, :integer, default: 0
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20191031173943) do
+ActiveRecord::Schema.define(version: 20191031210734) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -407,7 +407,6 @@ ActiveRecord::Schema.define(version: 20191031173943) do
     t.text     "description_drafting"
     t.text     "description_publishing_prices"
     t.text     "description_informing"
-    t.string   "help_link"
   end
 
   create_table "campaigns", force: :cascade do |t|
@@ -1485,8 +1484,6 @@ ActiveRecord::Schema.define(version: 20191031173943) do
     t.integer "budget/investments_count",                default: 0
     t.integer "legislation/proposals_count",             default: 0
     t.integer "legislation/processes_count",             default: 0
-    t.integer "budgets_count",                           default: 0
-    t.index ["budgets_count"], name: "index_tags_on_budgets_count", using: :btree
     t.index ["debates_count"], name: "index_tags_on_debates_count", using: :btree
     t.index ["legislation/processes_count"], name: "index_tags_on_legislation/processes_count", using: :btree
     t.index ["legislation/proposals_count"], name: "index_tags_on_legislation/proposals_count", using: :btree