SNOW-1058245-sqlalchemy-20-support: update skipped test docs

Failing tests classes added to test_suite.py for easier test invocation.

tests/sqlalchemy_test_suite/test_suite_20.py

@@ -82,8 +82,12 @@ def test_no_results_for_non_returning_insert(self, connection, style, executeman
 
 # road to 2.0
 class TrueDivTest(_TrueDivTest):
-    @pytest.mark.skip("Double slash is comment")
+    @pytest.mark.skip("`//` not supported")
     def test_floordiv_integer_bound(self, connection):
+        """Snowflake does not provide `//` arithmetic operator.
+
+        https://docs.snowflake.com/en/sql-reference/operators-arithmetic.
+        """
         pass