use absolute markdown link

Author: analogrelay

sdk/cosmos/azure_data_cosmos/CONTRIBUTING.md

@@ -2,7 +2,7 @@
 
 # Contributing to the Azure Cosmos DB SDK for Rust.
 
-First, review the Azure Core SDK Contributing guide: [CONTRIBUTING.md](../../../CONTRIBUTING.md).
+First, review the Azure Core SDK Contributing guide: [CONTRIBUTING.md](https://github.com/Azure/azure-sdk-for-rust/blob/main/CONTRIBUTING.md)
 
 ## Running Integration Tests