patch 8.2.3906: Vim9 help still contains "under development" warnings

Problem:    Vim9 help still contains "under development" warnings.
Solution:   Remove the explicit warning.
diff --git a/runtime/doc/vim9.txt b/runtime/doc/vim9.txt
index ced0c7d..47b6e03 100644
--- a/runtime/doc/vim9.txt
+++ b/runtime/doc/vim9.txt
@@ -1,17 +1,14 @@
-*vim9.txt*	For Vim version 8.2.  Last change: 2021 Dec 22
+*vim9.txt*	For Vim version 8.2.  Last change: 2021 Dec 26
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
 
 
-THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE
-
 Vim9 script commands and expressions.			*Vim9* *vim9*
 
 Most expression help is in |eval.txt|.  This file is about the new syntax and
 features in Vim9 script.
 
-THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE
 
 
 1.  What is Vim9 script?		|Vim9-script|
@@ -27,8 +24,6 @@
 
 1. What is Vim9 script?					*Vim9-script*
 
-THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE
-
 Vim script has been growing over time, while preserving backwards
 compatibility.  That means bad choices from the past often can't be changed
 and compatibility with Vi restricts possible solutions.  Execution is quite
@@ -76,8 +71,6 @@
 
 2. Differences from legacy Vim script			*vim9-differences*
 
-THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE
-
 Overview ~
 
 Brief summary of the differences you will most often encounter when using Vim9
@@ -354,7 +347,9 @@
 Although using a :def function probably works better.
 
 Declaring a variable with a type but without an initializer will initialize to
-zero, false or empty.
+false (for bool), empty (for string, list, dict, etc.) or zero (for number,
+any, etc.).  This matters especially when using the "any" type, the value will
+default to the number zero.
 
 In Vim9 script `:let` cannot be used.  An existing variable is assigned to
 without any command.  The same for global, window, tab, buffer and Vim
@@ -1067,8 +1062,6 @@
 
 3. New style functions					*fast-functions*
 
-THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE
-
 							*:def*
 :def[!] {name}([arguments])[: {return-type}]
 			Define a new function by the name {name}.  The body of
@@ -1184,8 +1177,6 @@
 
 4. Types					*vim9-types*
 
-THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE
-
 The following builtin types are supported:
 	bool
 	number
@@ -1366,8 +1357,6 @@
 5. Namespace, Import and Export
 					*vim9script* *vim9-export* *vim9-import*
 
-THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE
-
 A Vim9 script can be written to be imported.  This means that everything in
 the script is local, unless exported.  Those exported items, and only those
 items, can then be imported in another script.
@@ -1682,7 +1671,8 @@
 - TypeScript can use an expression like "99 || 'yes'" in a condition, but
   cannot assign the value to a boolean.  That is inconsistent and can be
   annoying.  Vim recognizes an expression with && or || and allows using the
-  result as a bool.  TODO: to be reconsidered
+  result as a bool.  The |falsy-operator| was added for the mechanism to use a
+  default value.
 - TypeScript considers an empty string as Falsy, but an empty list or dict as
   Truthy.  That is inconsistent.  In Vim an empty list and dict are also
   Falsy.
diff --git a/src/version.c b/src/version.c
index 719fe2a..8b9b27e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3906,
+/**/
     3905,
 /**/
     3904,