Add Clarification to pod_template_file exmaples (#12932)

Addresses https://github.com/apache/airflow/issues/11686

Clarifies why we have three files of pod_template_file examples

airflow/kubernetes/pod_template_file_examples/dags_in_image_template.yaml

@@ -14,6 +14,9 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
+#
+# This file is used for documentation purposes. Example can be found at docs/executor/kubernetes.rst
+#
 # [START template_with_dags_in_image]
 ---
 apiVersion: v1

airflow/kubernetes/pod_template_file_examples/dags_in_volume_template.yaml

@@ -14,6 +14,9 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
+#
+# This file is used for documentation purposes. Example can be found at docs/executor/kubernetes.rst
+#
 # [START template_with_dags_in_volume]
 ---
 apiVersion: v1

airflow/kubernetes/pod_template_file_examples/git_sync_template.yaml

@@ -14,8 +14,11 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
----
+#
+# This file is used for documentation purposes. Example can be found at docs/executor/kubernetes.rst
+#
 # [START git_sync_template]
+---
 apiVersion: v1
 kind: Pod
 metadata: