Issue #50: clarify packaging API key placeholders

clients/python/README.md

@@ -78,7 +78,7 @@ from mxgateway import GatewayClient
 
 async with await GatewayClient.connect(
     endpoint="localhost:5000",
-    api_key="mxgw_example",
+    api_key="<gateway-api-key>",
     plaintext=True,
 ) as client:
     session = await client.open_session(client_session_name="python-client")
@@ -141,7 +141,7 @@ Run live checks only when a gateway and MXAccess-backed worker are available:
 ```powershell
 $env:MXGATEWAY_INTEGRATION = '1'
 $env:MXGATEWAY_ENDPOINT = 'localhost:5000'
-$env:MXGATEWAY_API_KEY = 'mxgw_key_id_secret'
+$env:MXGATEWAY_API_KEY = '<gateway-api-key>'
 $env:MXGATEWAY_TEST_ITEM = 'Object.Attribute'
 mxgw-py smoke --endpoint $env:MXGATEWAY_ENDPOINT --plaintext --api-key-env MXGATEWAY_API_KEY --item $env:MXGATEWAY_TEST_ITEM --json
 ```