Revert upgrader back to original SQL (#2853)

Author: EricWittmann

app/src/main/java/io/apicurio/registry/storage/impl/sql/upgrader/ProtobufCanonicalHashUpgrader.java

@@ -47,7 +47,7 @@ public class ProtobufCanonicalHashUpgrader implements IDbUpgrader {
     @Override
     public void upgrade(Handle dbHandle) throws Exception {
 
-        String sql = "SELECT c.contentId, c.content, c.canonicalHash, c.contentHash, c.artifactreferences"
+        String sql = "SELECT c.contentId, c.content, c.canonicalHash, c.contentHash "
                 + "FROM versions v "
                 + "JOIN content c on c.contentId = v.contentId "
                 + "JOIN artifacts a ON v.tenantId = a.tenantId AND v.groupId = a.groupId AND v.artifactId = a.artifactId "