Indexer-multicore issue after block 1810000

in multicore mode, there is a bug between TEZOS_TOP=1810000 and TEZOS_TOP=2000000

Until fixed in the indexer, add the following to set a upper boundary for the indexer multicore script. TEZOS_TOP=1810000

Once it's fixed, remove this variable from the docker-compose.fast.yml (and only then close this current issue...)