Fix typo in running the AdService command (open-telemetry#1317)

Co-authored-by: Pierre Tessier <pierre@pierretessier.com>

Author: laithshadeed

src/adservice/README.md

@@ -21,7 +21,7 @@ To run the Ad Service:
 ```sh
 export AD_SERVICE_PORT=8080
 export FEATURE_FLAG_GRPC_SERVICE_ADDR=featureflagservice:50053
-./build/install/oteldemo/bin/AdService
+./build/install/opentelemetry-demo-ad-service/bin/AdService
 ```
 
 ### Upgrading Gradle