docs(email): remove duplicate CSS property from html (#2546)

- The CSS property 'text-decoration: none;' was duplicated in the example html code and is removed.

Author: srcnalt

www/docs/providers/email.md

@@ -187,7 +187,7 @@ const html = ({ url, site, email }) => {
       <td align="center" style="padding: 20px 0;">
         <table border="0" cellspacing="0" cellpadding="0">
           <tr>
-            <td align="center" style="border-radius: 5px;" bgcolor="${buttonBackgroundColor}"><a href="${url}" target="_blank" style="font-size: 18px; font-family: Helvetica, Arial, sans-serif; color: ${buttonTextColor}; text-decoration: none; text-decoration: none;border-radius: 5px; padding: 10px 20px; border: 1px solid ${buttonBorderColor}; display: inline-block; font-weight: bold;">Sign in</a></td>
+            <td align="center" style="border-radius: 5px;" bgcolor="${buttonBackgroundColor}"><a href="${url}" target="_blank" style="font-size: 18px; font-family: Helvetica, Arial, sans-serif; color: ${buttonTextColor}; text-decoration: none; border-radius: 5px; padding: 10px 20px; border: 1px solid ${buttonBorderColor}; display: inline-block; font-weight: bold;">Sign in</a></td>
           </tr>
         </table>
       </td>