Remove flags in language plugins (#8837)

* Remove flags in language plugins

* Remove references to language icons

* Remove obsolete example

There are no incoming links to this tiddler

* Remove icon from en-GB language

* Temporarily add all the languages for testing

To be removed before merging

* Add new "language" icon

* Languageswitcher update

* Translator editon docs update

* Fixes for introduction edition

* Remove LanguageGallery in ja-JP edition

* Remove temporary setting

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Co-authored-by: Jeremy Ruston <jeremy@jermolene.com>

core/ui/PageControls/language.tid

@@ -7,11 +7,7 @@ description: {{$:/language/Buttons/Language/Hint}}
 <span class="tc-popup-keep">
 <$button popup=<<qualify "$:/state/popup/language">> tooltip={{$:/language/Buttons/Language/Hint}} aria-label={{$:/language/Buttons/Language/Caption}} class=<<tv-config-toolbar-class>> selectedClass="tc-selected">
 <%if [<tv-config-toolbar-icons>match[yes]] %>
-    <span class="tc-image-button">
-        <$set name="languagePluginTitle" value={{$:/language}}>
-            <$image source=`$(languagePluginTitle)$/icon`/>
-        </$set>
-    </span>
+{{$:/core/images/language}}
 <%endif%>
 <%if [<tv-config-toolbar-text>match[yes]] %>
 <span class="tc-btn-text"><$text text={{$:/language/Buttons/Language/Caption}}/></span>