doc: Update reference table for current and upcoming release dates

Keep only 3 release dates, current and two upcoming. On the next release,
just update one, instead of multiple (zero point looking too much in the
future).

Signed-off-by: Donatas Abraitis <[email protected]>

doc/developer/workflow.rst

@@ -166,15 +166,15 @@ as early as possible, i.e. the first 2-week window.
 
 For reference, the expected release schedule according to the above is:
 
-+---------+------------+------------+------------+------------+------------+
-| Release | 2023-03-07 | 2023-07-04 | 2023-10-31 | 2024-02-27 | 2024-06-25 |
-+---------+------------+------------+------------+------------+------------+
-| RC      | 2023-02-21 | 2023-06-20 | 2023-10-17 | 2024-02-13 | 2024-06-11 |
-+---------+------------+------------+------------+------------+------------+
-| dev/X.Y | 2023-02-07 | 2023-06-06 | 2023-10-03 | 2024-01-30 | 2024-05-28 |
-+---------+------------+------------+------------+------------+------------+
-| freeze  | 2023-01-24 | 2023-05-23 | 2023-09-19 | 2024-01-16 | 2024-05-14 |
-+---------+------------+------------+------------+------------+------------+
++---------+------------+------------+------------+
+| Release | 2023-07-04 | 2023-10-31 | 2024-02-27 |
++---------+------------+------------+------------+
+| RC      | 2023-06-20 | 2023-10-17 | 2024-02-13 |
++---------+------------+------------+------------+
+| dev/X.Y | 2023-06-06 | 2023-10-03 | 2024-01-30 |
++---------+------------+------------+------------+
+| freeze  | 2023-05-23 | 2023-09-19 | 2024-01-16 |
++---------+------------+------------+------------+
 
 Here is the hint on how to get the dates easily: