Remove outdated Arbitrum support note (#121)

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: shane <shane@dune.com>

Author: 3 people

evm/defi-positions.mdx

@@ -17,7 +17,6 @@ Each position includes token holdings, USD valuations, underlying asset metadata
 <Note>
 This endpoint is currently available at the beta path (`/beta/evm/defi/positions`).
 Schemas are stable, but response fields may expand as we onboard new protocols.
-Also, **Arbitrum support is not currently available but is coming soon**.
 </Note>
 
 ## Supported Protocols