CLDR-17152 v44 BRS: update modification section (#3340)

Updates to modification section reflecting:
- CLDR-16937
- CLDR-16038
- CLDR-16249
- CLDR-16251

docs/ldml/tr35.md

@@ -4044,6 +4044,9 @@ Other contributors to CLDR are listed on the [CLDR Project Page](https://www.uni
     * [UnicodeSet syntax](#unicodeset-syntax)
     * [Backslash Escapes](#Backslash_Escapes)
     * [Variables in UnicodeSets](#Variables_in_UnicodeSets)
+  * [Unicode Language Identifier](#unicode-language-identifier): clarified constraint on duplicate subtags.
+  * [Key/Type Definitions](#key-and-type-definitions): clarified definition of `-dx`
+  * [EBNF](#ebnf): Clarified use of EBNF in LDML
 
 * [General](tr35-general.md#Contents)
   * Added new section [Unit Identifier Uniqueness](tr35-general.md#Unit_Identifier_Uniqueness), and added a relevant constraint on base_component in the [Syntax](tr35-general.md#syntax) section.