Cleanup settings migration

This just removes some more config values that aren't used anymore.
Not critical enough to warrant a new migration

farmbot_core/priv/config/migrations/20181203195326_migrate_settings.exs

@@ -30,5 +30,11 @@ defmodule FarmbotCore.Config.Repo.Migrations.MigrateSettings do
     delete_settings_config("api_migrated", :bool)
     delete_settings_config("firmware_needs_first_sync", :bool)
     delete_settings_config("first_boot", :bool)
+    delete_settings_config("authorized_ssh_key", :string)
+    delete_settings_config("firmware_hardware", :string)
+    delete_settings_config("first_party_farmware", :bool)
+    delete_settings_config("first_sync", :bool)
+    delete_settings_config("ssh_port", :float)
+    delete_settings_config("os_auto_update", :bool)
   end
 end

farmbot_core/priv/config/migrations/20181204173345_add_firmware_flash_setting.exs

@@ -4,7 +4,6 @@ defmodule FarmbotCore.Config.Repo.Migrations.AddFirmwareFlashSetting do
   import FarmbotCore.Config.MigrationHelpers
 
   def change do
-    update_config_value(:string, "settings", "firmware_hardware", nil)
     create_settings_config("firmware_needs_flash", :bool, true)
   end
 end

farmbot_core/priv/config/migrations/20190705203806_add_firmware_needs_open_flag.exs

@@ -4,7 +4,6 @@ defmodule FarmbotCore.Config.Repo.Migrations.AddFirmwareNeedsOpenFlag do
   import FarmbotCore.Config.MigrationHelpers
 
   def change do
-    update_config_value(:string, "settings", "firmware_hardware", nil)
     update_config_value(:bool, "settings", "firmware_needs_flash", true)
     create_settings_config("firmware_needs_open", :bool, false)
   end