Fix (or silence?) occasional postgrex connection error in tests

[taylordowns2000]

This doesn't result in test failures, but all the red text could be distracting or misleading to devs debugging other failing tests: 07:59:05.968 [error] Postgrex.Protocol (#PID<0.1793.0>) disconnected: ** (DBConnection.ConnectionError) client #PID<0.3956.0> exited

The logs are:

07:59:09.327 [error] Postgrex.Protocol (#PID<0.1798.0>) disconnected: ** (DBConnection.ConnectionError) owner #PID<0.5222.0> exited

Client #PID<0.5268.0> is still using a connection from owner at location:

    :prim_inet.recv0/3
    (postgrex 0.16.5) lib/postgrex/protocol.ex:3171: Postgrex.Protocol.msg_recv/4
    (postgrex 0.16.5) lib/postgrex/protocol.ex:2871: Postgrex.Protocol.recv_transaction/4
    (postgrex 0.16.5) lib/postgrex/protocol.ex:2180: Postgrex.Protocol.rebind_execute/4
    (ecto_sql 3.9.0) lib/ecto/adapters/sql/sandbox.ex:375: Ecto.Adapters.SQL.Sandbox.Connection.proxy/3
    (db_connection 2.4.2) lib/db_connection/holder.ex:354: DBConnection.Holder.holder_apply/4
    (db_connection 2.4.2) lib/db_connection.ex:1364: DBConnection.run_execute/5
    (db_connection 2.4.2) lib/db_connection.ex:1459: DBConnection.run/6
    (db_connection 2.4.2) lib/db_connection.ex:652: DBConnection.execute/4
    (ecto_sql 3.9.0) lib/ecto/adapters/postgres/connection.ex:102: Ecto.Adapters.Postgres.Connection.execute/4
    (ecto_sql 3.9.0) lib/ecto/adapters/sql.ex:850: Ecto.Adapters.SQL.execute!/5
    (ecto_sql 3.9.0) lib/ecto/adapters/sql.ex:820: Ecto.Adapters.SQL.execute/6
    (ecto 3.9.1) lib/ecto/repo/queryable.ex:229: Ecto.Repo.Queryable.execute/4
    (ecto 3.9.1) lib/ecto/repo/queryable.ex:19: Ecto.Repo.Queryable.all/3
    (ecto 3.9.1) lib/ecto/repo/preloader.ex:272: Ecto.Repo.Preloader.fetch_query/8
    (elixir 1.14.1) lib/task/supervised.ex:89: Task.Supervised.invoke_mfa/2
    (elixir 1.14.1) lib/task/supervised.ex:34: Task.Supervised.reply/4
    (stdlib 4.1.1) proc_lib.erl:240: :proc_lib.init_p_do_apply/3

The connection itself was checked out by #PID<0.5268.0> at location:

    (ecto_sql 3.9.0) lib/ecto/adapters/postgres/connection.ex:102: Ecto.Adapters.Postgres.Connection.execute/4
    (ecto_sql 3.9.0) lib/ecto/adapters/sql.ex:850: Ecto.Adapters.SQL.execute!/5
    (ecto_sql 3.9.0) lib/ecto/adapters/sql.ex:820: Ecto.Adapters.SQL.execute/6
    (ecto 3.9.1) lib/ecto/repo/queryable.ex:229: Ecto.Repo.Queryable.execute/4
    (ecto 3.9.1) lib/ecto/repo/queryable.ex:19: Ecto.Repo.Queryable.all/3
    (ecto 3.9.1) lib/ecto/repo/preloader.ex:272: Ecto.Repo.Preloader.fetch_query/8
    (elixir 1.14.1) lib/task/supervised.ex:89: Task.Supervised.invoke_mfa/2
    (elixir 1.14.1) lib/task/supervised.ex:34: Task.Supervised.reply/4
    (stdlib 4.1.1) proc_lib.erl:240: :proc_lib.init_p_do_apply/3