fixup! Editorial: Clarify operations related to merging locale data

Canonicalize localeId before updating languageId subtags, to avoid normative changes

For example, `new Intl.Locale("az-SU", {language: "ru"}).toString()`
should continue returning "ru-AZ" rather than "ru-RU".

https://github.com/tc39/ecma402/pull/804/files#r1295536807

spec/locale.html

@@ -31,6 +31,7 @@ <h1>Intl.Locale ( _tag_ [ , _options_ ] )</h1>
           1. Let _tag_ be ? ToString(_tag_).
         1. Set _options_ to ? CoerceOptionsToObject(_options_).
         1. If IsStructurallyValidLanguageTag(_tag_) is *false*, throw a *RangeError* exception.
+        1. Set _tag_ to CanonicalizeUnicodeLocaleId(_tag_).
         1. Set _tag_ to ? UpdateLanguageId(_tag_, _options_).
         1. Let _opt_ be a new Record.
         1. Let _calendar_ be ? GetOption(_options_, *"calendar"*, ~string~, ~empty~, *undefined*).
@@ -72,13 +73,13 @@ <h1>Intl.Locale ( _tag_ [ , _options_ ] )</h1>
     <emu-clause id="sec-updatelanguageid" type="abstract operation" oldids="sec-apply-options-to-tag">
       <h1>
         UpdateLanguageId (
-          _tag_: a language tag,
+          _tag_: a Unicode canonicalized locale identifier,
           _options_: an Object,
-        ): either a normal completion containing a String or a throw completion
+        ): either a normal completion containing a language tag or a throw completion
       </h1>
       <dl class="header">
         <dt>description</dt>
-        <dd>It updates the <code>unicode_language_id</code> subtags in _tag_ from the corresponding properties of _options_.</dd>
+        <dd>It updates the <code>unicode_language_id</code> subtags in _tag_ from the corresponding properties of _options_ and returns the <emu-xref href="#sec-isstructurallyvalidlanguagetag">structurally valid</emu-xref> but non-canonicalized result.</dd>
       </dl>
       <emu-alg>
         1. Let _languageId_ be the longest prefix of _tag_ matched by the <code>unicode_language_id</code> Unicode locale nonterminal.