fix: Pin Prophet dependency after breaking changes (#13852)

Prophet is heavily dependent on Pystan:
https://facebook.github.io/prophet/docs/installation.html

Pystan has recently (2021-03-25) release its v3.0.0.

This release is not backward compatible and breaks fbprophet:
https://github.com/facebook/prophet/issues/1856

(Indeed, fbprophet 0.6 specifies `pystan>=2.14` — but doesn't restrict
upgrading to next major release:
https://github.com/facebook/prophet/blob/0.6/python/requirements.txt#L3)

So we need to pin pystan to the lastest non 3.x release, while fbprophet
fixes the dependency on their side.

We have taken this opportunity to bump fbprophet too to its next minor
version.

Signed-off-by: Étienne Boisseau-Sierra <etienne.boisseau-sierra@unipart.io>

setup.py

@@ -144,7 +144,7 @@ setup(
         "postgres": ["psycopg2-binary==2.8.5"],
         "presto": ["pyhive[presto]>=0.4.0"],
         "trino": ["sqlalchemy-trino>=0.2"],
-        "prophet": ["fbprophet>=0.6, <0.7"],
+        "prophet": ["fbprophet>=0.7.1, <0.8", "pystan<3.0"],
         "redshift": ["sqlalchemy-redshift>=0.8.1, < 0.9"],
         "snowflake": ["snowflake-sqlalchemy>=1.2.3, <1.3"],
         "teradata": ["sqlalchemy-teradata==0.9.0.dev0"],