runtime(java): Optionally recognise all primitive constants in _switch-case_ labels

Define "g:java_syntax_previews" and include number 455 in
its list to enable this recognition:
------------------------------------------------------------
	let g:java_syntax_previews = [455]
------------------------------------------------------------

Reference:
https://openjdk.org/jeps/455

closes: #15698

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 7650433..01aa92a 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -1,4 +1,4 @@
-*syntax.txt*	For Vim version 9.1.  Last change: 2024 Sep 11
+*syntax.txt*	For Vim version 9.1.  Last change: 2024 Sep 18
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2176,10 +2176,11 @@
 withdrawn from this effort.  To cater for early adopters, there is optional
 support in Vim for syntax related preview features that are implemented.  You
 can request it by specifying a list of preview feature numbers as follows: >
-	:let g:java_syntax_previews = [430]
+	:let g:java_syntax_previews = [455]
 
 The supported JEP numbers are to be drawn from this table:
 	`430`: String Templates [JDK 21]
+	`455`: Primitive types in Patterns, instanceof, and switch
 
 Note that as soon as the particular preview feature will have been integrated
 into the Java platform, its entry will be removed from the table and related