Fix the unique index constraint index_hosts_on_url_unique in hosts table in VersionApp

Related gitlab-com/gl-infra/production#6660 (closed)

index_hosts_on_url_unique index was invalid.

We tried to recreated but we get an error

default=> CREATE UNIQUE INDEX CONCURRENTLY index_hosts_on_url_unique ON hosts (url);
ERROR:  could not create unique index "index_hosts_on_url_unique"
DETAIL:  Key (url)=(10.10.20.78) is duplicated.
CONTEXT:  parallel worker

Fix the broken unique constraint.

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