models: stop saving IP addresses in version tables.

Mark various `creator_ip_addr` and `updater_ip_addr` columns as ignored
and stop updating them in preparation for dropping them.

test/unit/note_test.rb

@@ -5,12 +5,10 @@ class NoteTest < ActiveSupport::TestCase
     setup do
       @user = FactoryBot.create(:user)
       CurrentUser.user = @user
-      CurrentUser.ip_addr = "127.0.0.1"
     end
 
     teardown do
       CurrentUser.user = nil
-      CurrentUser.ip_addr = nil
     end
 
     context "#merge_version" do
@@ -77,7 +75,6 @@ class NoteTest < ActiveSupport::TestCase
         assert_equal(1, @note.version)
         assert_equal(1, @note.versions.first.version)
         assert_equal(@user.id, @note.versions.first.updater_id)
-        assert_equal(CurrentUser.ip_addr, @note.versions.first.updater_ip_addr.to_s)
       end
 
       should "update the post's last_noted_at field" do
@@ -120,7 +117,6 @@ class NoteTest < ActiveSupport::TestCase
         assert_equal("fafafa", @note.versions.last.body)
         assert_equal(2, @note.version)
         assert_equal(@user.id, @note.versions.last.updater_id)
-        assert_equal(CurrentUser.ip_addr, @note.versions.last.updater_ip_addr.to_s)
       end
 
       context "without making any changes" do