Remove unnecessary url assign on form components

lib/livebook_web/live/home_live/import_content_component.ex

@@ -14,7 +14,6 @@ defmodule LivebookWeb.HomeLive.ImportContentComponent do
         Import notebook by directly pasting the <span class="font-semibold">live markdown</span> content.
       </p>
       <.form let={f} for={:data}
-        url="#"
         phx-submit="import"
         phx-change="validate"
         phx-target={@myself}

lib/livebook_web/live/home_live/import_url_component.ex

@@ -21,7 +21,6 @@ defmodule LivebookWeb.HomeLive.ImportUrlComponent do
         Paste the URL to a .livemd file, to a GitHub file, or to a Gist to import it.
       </p>
       <.form let={f} for={:data}
-        url="#"
         phx-submit="import"
         phx-change="validate"
         phx-target={@myself}

lib/livebook_web/live/session_live/attached_live.ex

@@ -40,7 +40,6 @@ defmodule LivebookWeb.SessionLive.AttachedLive do
         Then enter the connection information below:
       </p>
       <.form let={f} for={:data}
-        url="#"
         phx-submit="init"
         phx-change="validate"
         autocomplete="off"

lib/livebook_web/live/user_component.ex

@@ -28,7 +28,6 @@ defmodule LivebookWeb.UserComponent do
         <.user_avatar user={@preview_user} class="h-20 w-20" text_class="text-3xl" />
       </div>
       <.form let={f} for={:data}
-        url="#"
         phx-submit="save"
         phx-change="validate"
         phx-target={@myself}