docs: remove incorrect 'Handoff Arguments' Tip — UI section does not exist yet

The Tip block claimed the Vapi dashboard exposes function.parameters on
the handoff tool as a 'Handoff Arguments' section in the squad builder.
That section does not currently render. Verified two ways:

1. The string 'Handoff Arguments' appears nowhere in apps/dashboard
   (case-sensitive and case-insensitive grep, both with and without
   TS/TSX type filters).
2. apps/dashboard/src/features/squads/components/panels/sections/
   DestinationEditor.tsx (the component that renders the squad-builder
   handoff destination panel) only labels three sections: 'Context
   Engineering Plan', 'Variable Extraction Plan', and 'Description'.
   No 'Handoff Arguments' / 'Function Parameters' / JSON-schema editor.

The page also contradicted itself — the Warning earlier on the same
page (line 28) correctly states the squad builder does NOT carry
function.parameters through. The Warning is correct; the Tip was
aspirational, likely written assuming the squad-builder UX PR would
land before this docs PR, and is the outlier.

Removing the Tip rather than rewriting it because the existing Warning
already covers what readers need to know about dashboard support, so a
second callout restating it is redundant. When the squad-builder UX
ships, add a fresh callout pointing readers at the actual section name
(verified against the dashboard codebase at that time).

Author: dhruva-reddy

fern/squads/passing-data-between-assistants.mdx

@@ -72,10 +72,6 @@ The next assistant receives `customerIntent` and `customerSentiment` in the vari
 
 **Avoid this when** the value already exists somewhere structured (a prior tool result, the call's `customer.number`, etc.) — the model could mishear or paraphrase it. Use Approach 3 for those.
 
-<Tip>
-The Vapi dashboard exposes this as the **Handoff Arguments** section on the handoff tool config in the squad builder.
-</Tip>
-
 ## Approach 2: Variable extraction (`variableExtractionPlan.schema`)
 
 Define a `variableExtractionPlan.schema` on the handoff destination. After the handoff fires, Vapi makes a dedicated LLM call against the full conversation transcript to fill the schema, then merges the result into the variable bag for the next assistant.