i18n: Avoid using HTML tags in translation strings (wp-signup.php)

[ramiy]

The old translation 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.

Is using <a href="%1$s">%2$s</a>. This can be replaced with a simple %1$s moving the HTML tags out of the string. Making is much easier for translation, especially in RTL languages like Hebrew where bi-directional languages are difficult to handle.

[ramiy]

Old 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.

New string:

• %1$s is your new site. <a href="%2$s">Log in</a> as &#8220;%3$s&#8221; using your existing password.

[ramiy]

Related: #41645

[SergeyBiryukov]

In 41911:

I18N: Remove <a> tag from a translatable string in confirm_another_blog_signup().

Props ramiy.
Fixes #41694.