runtime(vim): Update base-syntax, improve Vim9 block start pattern

The opening curly brace must be followed by whitespace, comment or
trailing bar.

closes: #17454

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/testdir/input/vim9_block.vim

@@ -1,17 +1,18 @@
 vim9script
-
 # Vim9 blocks
+# VIM_TESTSETUP set list listchars=tab:> ,trail:-,extends:>,precedes:<,nbsp:+
 
 
 {
   var foo = 42
 }
 
+
 {
   {
     {
       {
-	var foo = 42
+        var foo = 42
       }
       var foo = 42
     }
@@ -20,6 +21,7 @@ vim9script
   var foo = 42
 }
 
+
 def Foo()
   {
     var foo = 42
@@ -27,7 +29,21 @@ def Foo()
   }
 enddef
 
-echo "foo" | {
-  var foo = 42
-}
+
+# start/end patterns
+
+{             
+  var foo = 42
+}             
+
+{ # comment
+  var foo = 42
+} # comment
+
+echo "Foo" | { | echo "Bar"
+  var foo = 42
+} | echo "Baz"
+
+# dictionary
+{}->items()