Don't list subsections of the Function chapter in the ToC

Author: stasm

guide/SUMMARY.md

@@ -13,11 +13,4 @@
 * [Comments](comments.md)
 * [Built-in Functions](builtins.md)
 * [Functions](functions.md)
-    * [Using Functions](functions.md#using-functions)
-    * [Parameters](functions.md#function-parameters)
-    * [Built-in Functions](functions.md#built-in-functions)
-        * [NUMBER](functions.md#number)
-        * [DATETIME](functions.md#datetime)
-    * [Implicit Use](functions.md#implicit-use)
-    * [Partial Arguments](functions.md#partial-arguments)
 * [Learn More](more.md)