docs(ins): add BASIC2-A to saving plan documentation (#5908)

Author: bene2k1

pages/billing/additional-content/understanding-savings-plans.mdx

@@ -123,7 +123,7 @@ The **Compute savings plan** can be used with the following resources, simultane
 
 The following resources are **not** covered by the savings plan discount:
 
-    - Instances H100, RENDER, L40S, L4, COPARM1, START1, X64, POP-WIN
+    - Instances H100, RENDER, L40S, L4, COPARM1, START1, X64, POP-WIN, BASIC2-A
 
 
 <Message type="important">