Update learn/infrastructure/relayer.md

Co-authored-by: Dawn Kelly <83190195+dawnkelly09@users.noreply.github.com>

Author: ilariae

learn/infrastructure/relayer.md

@@ -40,7 +40,7 @@ Client-side relaying relies on user-facing front ends, such as a webpage or a wa
 
 **Key Features**
 
-- **Cost-Efficiency** - users only pay the transaction fee for the second transaction, eliminating any additional costs
+- **Cost-efficiency** - users only pay the transaction fee for the second transaction, eliminating any additional costs
 - **No backend infrastructure** - the process is completely client-based, eliminating the need for a backend relaying infrastructure
 
 **Implementation**