LibWeb: Fix "incorrect behavior on select()" LadybirdBrowser#1446

This patch resolves the problem outlined in issue LadybirdBrowser#1446, where the
cursor_position node could be substituted with any other existing
node by the mousedown event. Previously, if this new node was not
equal to m_text_node, the function would return prematurely without
updating the selection.

With this fix, we ensure that the selection is properly updated in
such cases, rather than simply exiting the function.

Userland/Libraries/LibWeb/HTML/HTMLInputElement.cpp

@@ -2429,7 +2429,7 @@ HTMLInputElement::ValueAttributeMode HTMLInputElement::value_attribute_mode() co
 
 void HTMLInputElement::selection_was_changed(size_t selection_start, size_t selection_end)
 {
-    if (!m_text_node || !document().cursor_position() || document().cursor_position()->node() != m_text_node)
+    if (!m_text_node)
         return;
 
     document().set_cursor_position(DOM::Position::create(realm(), *m_text_node, selection_end));

Userland/Libraries/LibWeb/HTML/HTMLTextAreaElement.cpp

@@ -461,7 +461,7 @@ void HTMLTextAreaElement::queue_firing_input_event()
 
 void HTMLTextAreaElement::selection_was_changed(size_t selection_start, size_t selection_end)
 {
-    if (!m_text_node || !document().cursor_position() || document().cursor_position()->node() != m_text_node)
+    if (!m_text_node)
         return;
 
     document().set_cursor_position(DOM::Position::create(realm(), *m_text_node, selection_end));