Mark 3.1.55 as released (#21461)

Author: sbc100

ChangeLog.md

@@ -18,8 +18,11 @@ to browse the changes between the tags.
 
 See docs/process.md for more on how version tagging works.
 
-3.1.55 (in development)
+3.1.56 (in development)
 -----------------------
+
+3.1.55 - 03/01/24
+-----------------
 - Update sdl2-mixer port from 2.6.0 to 2.8.0
 - In `STRICT` mode the `HEAPXX` symbols (such as `HEAP8` and `HEAP32`) are now
   only exported on demand.  This means that they must be added to

emscripten-version.txt

@@ -1 +1 @@
-3.1.55-git
+3.1.56-git