Fix mypy command line options.

Signed-off-by: Juanjo Alvarez <[email protected]>

Author: Juanjo Alvarez

native/python_package/test/typecheck.sh

@@ -2,4 +2,4 @@
 # call this from the parent directory
 mypy --ignore-missing-imports --follow-imports silent --disallow-untyped-calls \
     --disallow-untyped-defs --check-untyped-defs --warn-unused-ignores \
-    --strict-optional --python-versio 3.6 python_driver/*.py
+    --strict-optional python_driver/*.py