runtime(doc): Fix enum example syntax

An ex-colon is not allowed before endenum.  As no other examples in the
file use an ex-colon remove them both.

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/vim9class.txt b/runtime/doc/vim9class.txt
index a06c2c6..9aab6c7 100644
--- a/runtime/doc/vim9class.txt
+++ b/runtime/doc/vim9class.txt
@@ -1,4 +1,4 @@
-*vim9class.txt*	For Vim version 9.1.  Last change: 2024 Nov 11
+*vim9class.txt*	For Vim version 9.1.  Last change: 2024 Dec 29
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -951,11 +951,11 @@
 						*enum* *E1418* *E1419* *E1420*
 An enum is a type that can have one of a list of values.  Example: >
 
-    :enum Color
+    enum Color
 	White,
 	Red,
 	Green, Blue, Black
-    :endenum
+    endenum
 <
 						*enumvalue* *E1422*
 The enum values are separated by commas.  More than one enum value can be