Update shimmer-token.md

SMR is not available on Bitfinex anymore. 
SMR is available on MEXC.

Author: Schnurzle

docs/get-started/introduction/shimmer/shimmer-token.md

@@ -57,7 +57,7 @@ overall ecosystem's development.
 
 You can buy Shimmer tokens currently on the following exchanges and marketplaces:
 
-- [Bitfinex](https://bitfinex.com)
+- [MEXC](https://www.mexc.com)
 - [Iotabee](https://iotabee.com/swap)
 - [ShimmerSea](https://shimmersea.finance/swap)
 - [Soonaverse](https://soonaverse.com/tokens/all)