runtime(fortran): update syntax and documentation (#13912)

* runtime (doc): update Fortran section
* runtime(syntax): Complete support for Fortran 2023.
   Minor improvements.

Signed-off-by: Ajit-Thakkar <142174202+Ajit-Thakkar@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index a2377b5..c4f59ae 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 Jan 23
+*syntax.txt*	For Vim version 9.1.  Last change: 2024 Jan 24
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -1594,13 +1594,11 @@
 FORTRAN					*fortran.vim* *ft-fortran-syntax*
 
 Default highlighting and dialect ~
-Vim highlights according to Fortran 2023 (the most recent standard) by
-default.  This choice should be appropriate for most users most of the time
-because Fortran 2023 is almost a superset of previous versions (Fortran 2018,
-2008, 2003, 95, 90, and 77).  A small number of features new to Fortran 2018
-and Fortran 2023 may have been omitted at present; the transition to Fortran
-2023 will be completed in the near future. A few legacy constructs deleted or
-declared obsolescent in recent Fortran standards are highlighted as todo
+Vim highlights according to Fortran 2023 (the most recent standard). This
+choice should be appropriate for most users most of the time because Fortran
+2023 is almost a superset of previous versions (Fortran 2018, 2008, 2003, 95,
+90, 77, and 66).  A few legacy constructs deleted or declared obsolescent,
+respectively, in recent Fortran standards are highlighted as errors and todo
 items.
 
 The syntax script no longer supports Fortran dialects.  The variable