pin dbt to <0.19.0 in dbt example

Summary: This likely points to a breakage in dagster-dbt, but currently only the dbt example tests are failing.  More info here: #3616.

Test Plan: bk

Reviewers: bob, max, johann

Reviewed By: johann

Subscribers: johann

Differential Revision: https://dagster.phacility.com/D6189

examples/dbt_example/dbt_example_tests/test_pipeline.py

@@ -45,6 +45,5 @@ def test_pipeline(pg_hostname, postgres):  # pylint: disable=unused-argument
                         "io_manager": {"config": {"base_dir": temp_dir}},
                     },
                 },
-                raise_on_error=False,
             )
             assert res.success

examples/dbt_example/setup.py

@@ -14,7 +14,7 @@
         "dagster-postgres",
         "dagster-slack",
         "dagstermill",
-        "dbt",
+        "dbt < 0.19.0",
     ],
     author="Elementl",
     license="Apache-2.0",