DOC: mention in INSTALL that it's development again

This reverts commit 975908c831f8fa00ccf1afd1f7cfe2ad80a8c8e6.
diff --git a/INSTALL b/INSTALL
index 59e66c6..32cf5d9 100644
--- a/INSTALL
+++ b/INSTALL
@@ -1,15 +1,15 @@
 Installation instructions for HAProxy
 =====================================
 
-HAProxy 2.3 is a stable version, which means that it will get fixes for bugs as
-they are discovered till around Q1 2022 and should not receive new features.
-This version is mostly suited at experienced users who are willing to quickly
-follow updates. New users are encouraged to use long term supported versions
-such as the ones provided by their software vendor or Linux distribution, as
-such versions require far less common updates. If for any reason you'd prefer
-a different version than the one packaged for your system, you want to be
-certain to have all the fixes or to get some commercial support, other choices
-are available at https://www.haproxy.com/.
+This is a development version, so it is expected to break from time to time,
+to add and remove features without prior notification and it should not be used
+in production. If you are not used to build from sources or if you are not used
+to follow updates then it is recommended that instead you use the packages
+provided by your software vendor or Linux distribution. Most of them are taking
+this task seriously and are doing a good job at backporting important fixes. If
+for any reason you'd prefer to use a different version than the one packaged
+for your system, you want to be certain to have all the fixes or to get some
+commercial support, other choices are available at http://www.haproxy.com/.
 
 
 Areas covered in this document