iteritems -> items (#12629)

### Summary & Motivation

Fixes #12604

`.iteritems` is [deprecated since 1.50
](https://pandas.pydata.org/docs/whatsnew/v1.5.0.html#other-deprecations)
and will be removed in a future version. Changing to `.items`.
(pandas-dev/pandas#45321).

### How I Tested These Changes

I did not, but pandas-dev/pandas#45321 appears
to indicate it's a safe change to make. If I can somehow install this
version of dagster on my machine, I'm happy to test using the code that
surfaced the issue, but I'm not sure how to do that.

python_modules/libraries/dagster-snowflake-pandas/dagster_snowflake_pandas/snowflake_pandas_type_handler.py

@@ -76,8 +76,8 @@ def handle_output(
             "dataframe_columns": MetadataValue.table_schema(
                 TableSchema(
                     columns=[
-                        TableColumn(name=name, type=str(dtype))
-                        for name, dtype in obj.dtypes.iteritems()
+                        TableColumn(name=str(name), type=str(dtype))
+                        for name, dtype in obj.dtypes.items()
                     ]
                 )
             ),