Qt/Search: Simplify placeholder text

A search box is a common UI element. We don't need to explicitly tell
the user that they need to type a search term. Also,

Let's use the common "Search <items>..." placeholder text instead
and make the string shorter for localisation.

Source/Core/DolphinQt2/SearchBar.cpp

@@ -24,7 +24,7 @@ void SearchBar::CreateWidgets()
   m_search_edit = new QLineEdit;
   m_close_button = new QPushButton(tr("Close"));
 
-  m_search_edit->setPlaceholderText(tr("Type your search term here"));
+  m_search_edit->setPlaceholderText(tr("Search games..."));
 
   auto* layout = new QHBoxLayout;