patch 9.1.1039: Vim9: comments are outdated

Problem:  Vim9: comments are outdated
Solution: Update comments, and include an enum example in the help
          (Yegappan Lakshmanan)

closes: #16485

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/eval.c b/src/eval.c
index 306cfe7..387f61d 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3994,7 +3994,7 @@
 }
 
 /*
- * Handle the bitwise left/right shift operator expression:
+ * Handle fourth level expression (bitwise left/right shift operators):
  *	var1 << var2
  *	var1 >> var2
  *
@@ -4512,7 +4512,8 @@
 }
 
 /*
- * Handle a type cast before a base level expression.
+ * Handle seventh level expression:
+ *	a type cast before a base level expression.
  * "arg" must point to the first non-white of the expression.
  * "arg" is advanced to just after the recognized expression.
  * Return OK or FAIL.
@@ -4883,7 +4884,7 @@
 }
 
 /*
- * Handle sixth level expression:
+ * Handle eighth level expression:
  *  number		number constant
  *  0zFFFFFFFF		Blob constant
  *  "string"		string constant