docs(tutorial/step_09): note about 'Filter' suffix

Request Type: docs

How to reproduce: 

Component(s): misc core

Impact: small

Complexity: small

This issue is related to: 

**Detailed Description:**

The tutorial left out the fact that 'Filter' was appended to filter names when injected into unit tests. Will save some people time to remind them here in this step.

**Other Comments:**

Reminder that 'Filter' is appended to filter names when injected. Link to Filter guide where this is mentioned.