Avoid using HTML tags in translation strings (wp-signup.php)

[ramiy]

The wp-signup.php file has lots of translation strings.

The attached patch includes:

1. Eight new translators comments.

2. Removed HTML tags.

---

I've removed the HTML tags from this string:
<a href="%1$s">%2$s</a> is your new site. <a href="%3$s">Log in</a> as &#8220;%4$s&#8221; using your existing password.

By splitting the string into two smaller strings:

1. %s is your new site.

2. <a href="%1$s">Log in</a> as &#8220;%2$s&#8221; using your existing password.

[ocean90]

In 37551:

I18N: Add translators comments to wp-signup.php.

Props ramiy.
Fixes #35730.