docs(docker-compose): Update examples to not use vars in keys

docker-compose/examples/hashicorpvault/docker-compose.yml

@@ -3,7 +3,7 @@ services:
         image: "hashicorpvault:${HASHICORPVAULT_VERSION}"
         container_name: "hashicorpvault-${CONTEXT}"
         networks:
-            hashicorpvault-${CONTEXT}:
+            hashicorpvault-default:
         extends:
             file: common-settings.yml
             service: common-settings
@@ -17,7 +17,7 @@ services:
             # HASHICORPVAULT_USER: ${HASHICORPVAULT_USER}
             # HASHICORPVAULT_PASSWORD: ${HASHICORPVAULT_PASSWORD}
 networks:
-    hashicorpvault-${CONTEXT}:
+    hashicorpvault-default:
         name: hashicorpvault-${CONTEXT}
         driver: bridge
         driver_opts: