README.md in field_test-0.5.4 vs README.md in field_test-0.5.5

@@ -330,79 +330,9 @@
 
 ```ruby
 user.field_test_memberships
 ```
 
-## Upgrading
-
-### 0.3.0
-
-Upgrade the gem and add to `config/field_test.yml`:
-
-```yml
-legacy_participants: true
-```
-
-Also, if you use Field Test in emails, know that the default way participants are determined has changed. Restore the previous way with:
-
-```ruby
-class ApplicationMailer < ActionMailer::Base
-  def field_test_participant
-    message.to.first
-  end
-end
-```
-
-We also recommend upgrading participants when you have time.
-
-#### Upgrading Participants
-
-Field Test 0.3.0 splits the `field_test_memberships.participant` column into `participant_type` and `participant_id`.
-
-To upgrade without downtime, create a migration:
-
-```sh
-rails generate migration upgrade_field_test_participants
-```
-
-with:
-
-```ruby
-class UpgradeFieldTestParticipants < ActiveRecord::Migration[6.0]
-  def change
-    add_column :field_test_memberships, :participant_type, :string
-    add_column :field_test_memberships, :participant_id, :string
-
-    add_index :field_test_memberships, [:participant_type, :participant_id, :experiment],
-      unique: true, name: "index_field_test_memberships_on_participant_and_experiment"
-  end
-end
-```
-
-After you run it, writes will go to both the old and new sets of columns.
-
-Next, backfill data:
-
-```ruby
-FieldTest::Membership.where(participant_id: nil).find_each do |membership|
-  participant = membership.participant
-
-  if participant.include?(":")
-    participant_type, _, participant_id = participant.rpartition(":")
-    participant_type = nil if participant_type == "cookie" # legacy
-  else
-    participant_id = participant
-  end
-
-  membership.update!(
-    participant_type: participant_type,
-    participant_id: participant_id
-  )
-end
-```
-
-Finally, remove `legacy_participants: true` from the config file. Once you confirm it’s working, you can drop the `participant` column (you can rename it first just to be extra safe).
-
 ## Credits
 
 A huge thanks to [Evan Miller](https://www.evanmiller.org/) for deriving the Bayesian formulas.
 
 ## History