Update docker image python version to 3.7 in entrypoint doc (apache#2…

…9964)

docs/docker-stack/entrypoint.rst

@@ -132,7 +132,7 @@ if you specify extra arguments. For example:
 
 .. code-block:: bash
 
-  docker run -it apache/airflow:2.6.0.dev0-python3.6 bash -c "ls -la"
+  docker run -it apache/airflow:2.6.0.dev0-python3.7 bash -c "ls -la"
   total 16
   drwxr-xr-x 4 airflow root 4096 Jun  5 18:12 .
   drwxr-xr-x 1 root    root 4096 Jun  5 18:12 ..
@@ -144,21 +144,21 @@ you pass extra parameters. For example:
 
 .. code-block:: bash
 
-  > docker run -it apache/airflow:2.6.0.dev0-python3.6 python -c "print('test')"
+  > docker run -it apache/airflow:2.6.0.dev0-python3.7 python -c "print('test')"
   test
 
 If first argument equals to "airflow" - the rest of the arguments is treated as an airflow command
 to execute. Example:
 
 .. code-block:: bash
 
-   docker run -it apache/airflow:2.6.0.dev0-python3.6 airflow webserver
+   docker run -it apache/airflow:2.6.0.dev0-python3.7 airflow webserver
 
 If there are any other arguments - they are simply passed to the "airflow" command
 
 .. code-block:: bash
 
-  > docker run -it apache/airflow:2.6.0.dev0-python3.6 help
+  > docker run -it apache/airflow:2.6.0.dev0-python3.7 help
     usage: airflow [-h] GROUP_OR_COMMAND ...
 
     positional arguments: