README updated with the release of Ansible Core 2.19

* https://docs.ansible.com/ansible/devel/roadmap/ROADMAP_2_19.html

Signed-off-by: saito-hideki <saito@fgrep.org>

README.md

@@ -46,10 +46,10 @@ To upgrade the collection to the latest available version, run the following com
 ansible-galaxy collection install ansible.posix --upgrade
 ```
 
-You can also install a specific version of the collection, for example, if you need to downgrade when something is broken in the latest version (please report an issue in this repository). Use the following syntax to install version 1.0.0:
+You can also install a specific version of the collection, for example, if you need to downgrade when something is broken in the latest version (please report an issue in this repository). Use the following syntax to install version 2.0.0:
 
 ```shell
-ansible-galaxy collection install ansible.posix:==1.0.0
+ansible-galaxy collection install ansible.posix:==2.0.0
 ```
 
 See [using Ansible collections](https://docs.ansible.com/ansible/devel/user_guide/collections_using.html) for more details.
@@ -78,11 +78,10 @@ ansible-doc -t callback ansible.posix.profile_tasks
 
 The following ansible-core versions have been tested with this collection:
 
-- ansible-core 2.19 (devel)
-- ansible-core 2.18 (stable) *
+- ansible-core 2.20 (devel)
+- ansible-core 2.19 (stable) *
+- ansible-core 2.18 (stable)
 - ansible-core 2.17 (stable)
-- ansible-core 2.16 (stable)
-- ansible-core 2.15 (stable)
 
 ## Contributing