kola/README-kola-ext.md: fix `platforms` example
The key there is a space-separated list of platform names, not a JSON
list directly.
@@ -121,7 +121,7 @@ inline per test, like this:
```sh
#!/bin/bash
set -xeuo pipefail
-# kola: { "architectures": "x86_64", "platforms": ["aws", "gcp"] }
+# kola: { "architectures": "x86_64", "platforms": "aws gcp"] }
test code here
```
