Fix subject-verb agreement: use "subset" with "is"

Agent-Logs-Url: https://github.com/Kong/developer.konghq.com/sessions/8be40d68-4447-4c4c-a3f2-87ae4c7ce415

Co-authored-by: juliamrch <101819212+juliamrch@users.noreply.github.com>

Author: Copilot

app/insomnia/dynamic-mocking.md

@@ -54,7 +54,7 @@ rows:
   - option: Apply conditional logic
     description: |
       Use simple Liquid conditions to vary the response based on the request.  
-      Only a limited set of Liquid tags is supported for safety.
+      Only a limited subset of Liquid tags is supported for safety.
   - option: Generate fake data
     description: |
       Insert random but realistic data, such as names, emails, or timestamps using faker variables.