LibWeb: Fix a few const-ness issues

Author: https://github.com/mattco98
Commit: c0b2fa74ac
Pull-request: https://github.com/SerenityOS/serenity/pull/17620
Issue: https://github.com/SerenityOS/serenity/issues/16988
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibWeb/HTML/EventLoop/Task.cpp

@@ -9,7 +9,7 @@
 
 namespace Web::HTML {
 
-Task::Task(Source source, DOM::Document* document, JS::SafeFunction<void()> steps)
+Task::Task(Source source, DOM::Document const* document, JS::SafeFunction<void()> steps)
     : m_source(source)
     , m_steps(move(steps))
     , m_document(JS::make_handle(document))
@@ -30,11 +30,6 @@ bool Task::is_runnable() const
     return !m_document.ptr() || m_document->is_fully_active();
 }
 
-DOM::Document* Task::document()
-{
-    return m_document.ptr();
-}
-
 DOM::Document const* Task::document() const
 {
     return m_document.ptr();