Mark 3.4 branch as stable, release is imminent

(cherry picked from commit ba65652fae73dfab1c3d8aa9bbfb4bd36d99b935)

about/release_policy.rst

@@ -90,9 +90,12 @@ on GitHub.
 +-------------+----------------------+--------------------------------------------------------------------------+
 | Godot 4.0   | ~2022 (see below)    | |unstable| *Current focus of development (unstable).*                    |
 +-------------+----------------------+--------------------------------------------------------------------------+
-| Godot 3.4   | Q4 2021              | |supported| *Beta.* Receives new features as well as bug fixes while     |
+| Godot 3.5   | Q1 2022              | |supported| *Beta.* Receives new features as well as bug fixes while     |
 |             |                      | under development.                                                       |
 +-------------+----------------------+--------------------------------------------------------------------------+
+| Godot 3.4   | November 2021        | |supported| Receives fixes for bugs, security and platform support       |
+|             |                      | issues, as well as backwards-compatible usability enhancements.          |
++-------------+----------------------+--------------------------------------------------------------------------+
 | Godot 3.3   | April 2021           | |supported| Receives fixes for bugs, security and platform support       |
 |             |                      | issues, as well as backwards-compatible usability enhancements.          |
 +-------------+----------------------+--------------------------------------------------------------------------+