refactor(pdfjs-viewer): remove deprecated handwriting fonts and related options

Deleted outdated handwriting font definitions from viewer.css and removed associated options from viewer.html and viewer.mjs. This streamlines the font selection process for typed signatures, focusing on standard fonts.

public/pdfjs-viewer/viewer.html

@@ -651,8 +651,6 @@ See https://github.com/adobe-type-tools/cmap-resources
                   <label for="signatureFontSelect">Font:</label>
                   <select id="signatureFontSelect" tabindex="0">
                     <option value="cursive">Cursive (Default)</option>
-                    <option value="PingFang">PingFang (Handwriting)</option>
-                    <option value="Qiantu">Qiantu (Handwriting)</option>
                     <option value="Kalam">Kalam</option>
                     <option value="Sacramento">Sacramento</option>
                     <option value="AlexBrush">AlexBrush</option>