test: Use t3 instead of t2 instances (#251)

Use t3 instead of t2 instances

Issue #, if available: n/a

Description of changes:

As title says.

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

Author: ananth102

test/e2e/replacement_values.py

@@ -250,6 +250,6 @@
         get_region(), "ml.m4.xlarge"
     ),
     "NOTEBOOK_INSTANCE_INSTANCE_TYPES": NOTEBOOK_INSTANCE_INSTANCE_TYPES.get(
-        get_region(), "ml.t2.medium"
+        get_region(), "ml.t3.medium"
     ),
 }