Fixed failed tests on Kokoro (Natural Language API) [(#1185)](GoogleCloudPlatform/python-docs-samples#1185)

* Add Snippet for Listing All Subscriptions in a Project

* Fixed the failed tests on Kokoro

classify_text_tutorial_test.py::test_query_text
classify_text_tutorial_test.py::test_query_category

Author: michaelawyu

samples/snippets/classify_text/classify_text_tutorial.py

@@ -133,8 +133,8 @@ def similarity(categories1, categories2):
     categories1 = split_labels(categories1)
     categories2 = split_labels(categories2)
 
-    norm1 = numpy.linalg.norm(categories1.values())
-    norm2 = numpy.linalg.norm(categories2.values())
+    norm1 = numpy.linalg.norm(list(categories1.values()))
+    norm2 = numpy.linalg.norm(list(categories2.values()))
 
     # Return the smallest possible similarity if either categories is empty.
     if norm1 == 0 or norm2 == 0: