Work-around for migration V4_0_3__Add_Index_To_Oauth_Code failure

FixLegacyMySQLOauthCodeColumn.sql

-- Prior to UAA 1.5.2, the UAA schema would create the oauth_code.code column as
-- VARCHAR(256).  A recent migration V4_0_3__Add_Index_To_Oauth_Code attempts to
-- add a unique index to this column to improve lookup speed, but the VARCHAR(256)
-- column in these long-lived UAA databases is too large for InnoDB to uniquely
-- index. If your deployment experiences failure in the UAA job when updating to
-- CF v255, this manual intervention should repair the UAA database by resizing
-- the column so that the migration can succeed on the next attempt.

DELETE FROM schema_version WHERE version = '4.0.3';
ALTER TABLE oauth_code MODIFY code VARCHAR(255);