Fix documentation around downward API

Author: psx95

gcp-resources/README.md

@@ -14,9 +14,9 @@ The following OpenTelemetry semantic conventions will be detected:
 | host.id                 | auto                                         | auto                                                   |                                          |                                                |                                                |
 | host.name               | auto                                         | auto                                                   |                                          |                                                |                                                |
 | host.type               | auto                                         | auto                                                   |                                          |                                                |                                                |
-| k8s.pod.name            |                                              | environment variable                                   |                                          |                                                |                                                |
-| k8s.namespace.name      |                                              | environment variable                                   |                                          |                                                |                                                |
-| k8s.container.name      |                                              | environment variable                                   |                                          |                                                |                                                |
+| k8s.pod.name            |                                              | downward API                                           |                                          |                                                |                                                |
+| k8s.namespace.name      |                                              | downward API                                           |                                          |                                                |                                                |
+| k8s.container.name      |                                              | hardcoded                                              |                                          |                                                |                                                |
 | k8s.cluster.name        |                                              | auto                                                   |                                          |                                                |                                                |
 | faas.name               |                                              |                                                        | auto                                     | auto                                           | auto                                           |
 | faas.version            |                                              |                                                        | auto                                     | auto                                           | auto                                           |