Update migrations for Rubocop

Not sure why this didn’t crop up locally, but CI’s definitely not happy
without these changes.

db/migrate/20200524062158_relax_provider_columns.rb

@@ -2,16 +2,20 @@
 
 class RelaxProviderColumns < ActiveRecord::Migration[6.0]
   def up
-    change_column_null :fans, :provider, true
-    change_column_null :fans, :provider_identity, true
+    change_table :fans, :bulk => true do |t|
+      t.change_null :provider, true
+      t.change_null :provider_identity, true
 
-    change_column_null :fans, :email, false
+      t.change_null :email, false
+    end
   end
 
   def down
-    change_column_null :fans, :provider, false
-    change_column_null :fans, :provider_identity, false
+    change_table :fans, :bulk => true do |t|
+      t.change_null :provider, false
+      t.change_null :provider_identity, false
 
-    change_column_null :fans, :email, true
+      t.change_null :email, true
+    end
   end
 end

db/migrate/20200824120413_split_album_urls.rb

@@ -3,9 +3,11 @@
 class SplitAlbumUrls < ActiveRecord::Migration[6.0]
   # rubocop:disable Metrics/MethodLength
   def up
-    rename_column :albums, :url, :last_fm_url
-    change_column_null :albums, :last_fm_url, true
-    add_column :albums, :spotify_url, :string
+    change_table :albums, :bulk => true do |t|
+      t.rename_column :url, :last_fm_url
+      t.change_null :last_fm_url, true
+      t.add_column :spotify_url, :string
+    end
 
     execute <<~SQL.squish
       UPDATE albums
@@ -26,8 +28,10 @@ def down
       WHERE spotify_url IS NOT NULL
     SQL
 
-    remove_column :albums, :spotify_url
-    change_column_null :albums, :last_fm_url, false
-    rename_column :albums, :last_fm_url, :url
+    change_table :albums, :bulk => true do |t|
+      t.remove_column :spotify_url
+      t.change_null :last_fm_url, false
+      t.rename_column :last_fm_url, :url
+    end
   end
 end

db/migrate/20200824121128_split_artist_urls.rb

@@ -3,9 +3,11 @@
 class SplitArtistUrls < ActiveRecord::Migration[6.0]
   # rubocop:disable Metrics/MethodLength
   def up
-    rename_column :artists, :url, :last_fm_url
-    change_column_null :artists, :last_fm_url, true
-    add_column :artists, :spotify_url, :string
+    change_table :artists, :bulk => true do |t|
+      t.rename_column :url, :last_fm_url
+      t.change_null :last_fm_url, true
+      t.add_column :spotify_url, :string
+    end
 
     execute <<~SQL.squish
       UPDATE artists
@@ -26,8 +28,10 @@ def down
       WHERE spotify_url IS NOT NULL
     SQL
 
-    remove_column :artists, :spotify_url
-    change_column_null :artists, :last_fm_url, false
-    rename_column :artists, :last_fm_url, :url
+    change_table :artists, :bulk => true do |t|
+      t.remove_column :spotify_url
+      t.change_null :last_fm_url, false
+      t.rename_column :last_fm_url, :url
+    end
   end
 end