DEV: Remove unused admin-theme-item modal (#23233)

app/assets/javascripts/admin/addon/templates/modal/admin-theme-item.hbs

@@ -1,26 +0,0 @@
-<div class="popular-theme-item">
-  <div class="popular-theme-name">
-    {{this.theme.name}}
-    {{#if this.theme.preview}}
-      <a
-        href={{this.theme.preview}}
-        title="Preview"
-        rel="noopener noreferrer"
-        target="_blank"
-      >{{d-icon "far-eye"}}</a>
-    {{/if}}
-  </div>
-  <div class="popular-theme-buttons">
-    {{#if this.theme.installed}}
-      <span>{{i18n "admin.customize.theme.installed"}}</span>
-    {{else}}
-      <DButton
-        @class="btn-small"
-        @label="admin.customize.theme.install"
-        @disabled={{this.installDisabled}}
-        @icon="upload"
-        @action={{action "installThemeFromList" this.theme.value}}
-      />
-    {{/if}}
-  </div>
-</div>

app/assets/javascripts/discourse/app/services/modal.js

@@ -46,7 +46,6 @@ const KNOWN_LEGACY_MODALS = [
   "topic-summary",
   "user-status",
   "admin-reseed",
-  "admin-theme-item",
   "admin-color-scheme-select-base",
   "admin-form-template-validation-options",
   "admin-staff-action-log-details",