Simplify localization of the "default-content" in FreeText editors

By using "data-l10n-attrs" it's possible to instruct Fluent to localize *custom* attributes, which means that we don't need to manually translate/update the "default-content" in FreeText editors.

l10n/en-US/viewer.ftl

@@ -348,9 +348,9 @@ pdfjs-editor-free-highlight-thickness-input = Thickness
 pdfjs-editor-free-highlight-thickness-title =
     .title = Change thickness when highlighting items other than text
 
-pdfjs-free-text =
+pdfjs-free-text2 =
     .aria-label = Text Editor
-pdfjs-free-text-default-content = Start typing…
+    .default-content = Start typing…
 pdfjs-ink =
     .aria-label = Draw Editor
 pdfjs-ink-canvas =

src/display/editor/freetext.js

@@ -139,9 +139,7 @@ class FreeTextEditor extends AnnotationEditor {
 
   /** @inheritdoc */
   static initialize(l10n, uiManager) {
-    AnnotationEditor.initialize(l10n, uiManager, {
-      strings: ["pdfjs-free-text-default-content"],
-    });
+    AnnotationEditor.initialize(l10n, uiManager);
     const style = getComputedStyle(document.documentElement);
 
     if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
@@ -563,12 +561,10 @@ class FreeTextEditor extends AnnotationEditor {
     this.editorDiv.className = "internal";
 
     this.editorDiv.setAttribute("id", this.#editorDivId);
-    this.editorDiv.setAttribute("data-l10n-id", "pdfjs-free-text");
+    this.editorDiv.setAttribute("data-l10n-id", "pdfjs-free-text2");
+    this.editorDiv.setAttribute("data-l10n-attrs", "default-content");
     this.enableEditing();
 
-    AnnotationEditor._l10nPromise
-      .get("pdfjs-free-text-default-content")
-      .then(msg => this.editorDiv?.setAttribute("default-content", msg));
     this.editorDiv.contentEditable = true;
 
     const { style } = this.editorDiv;