As far as I know, the only way to remove that would be to edit the actual html for the login page. The location of the file you want depends on if you are/aren't using LFDS Authentication (SSO).

If you are using SSO

there should be a folder like (depending on your install path). Note: unless you installed a separate Security Token Service on your web app server, this file would actually reside on the Directory Server.

C:\Program Files\Laserfiche\Directory Server\Web\WebSTS\Views\Home

If you are not using SSO 

It would be a similar file/folder somewhere in the application folders on the server hosting Forms/Web Client (see this post for more information)

Inside, there should be a Login.cshtml file for the login page.

In the file you could use CSS or JavaScript to hide the "forgotPasswordSection" container, or everything with the "forgot" class.

<div style="text-align: center; margin-top: 10px;" id="forgotPasswordSection">
	<a href="#" class="forgot" onclick="forgotPassword()" id="ForgotPasswordStr"></a>
</div>

The most straightforward way might be to just add display:none; right in the inline style settings, but there's at least 3 or 4 other ways you could do it with CSS or JavaScript.

However, make sure you only hide the element rather than deleting it outright. There's code that references that object so removing it could cause errors.

The only major catch is that you would need to redo this every time you upgrade.