gui2/title_screen: Make Version label formatted and translatable

Closes #2914.

This doesn't break the string freeze since it reuses a format string
from the same textdomain required by gui2/game_version for the exact
same purpose.

(cherry-picked from commit fa15142)

changelog.md

@@ -33,6 +33,7 @@
    * Fixed "Search" placeholder text in dialog item filters not being
      translatable (bug #2709, bug #2732).
    * Fixed Logging Options tooltips not being translatable (bug #2837).
+   * Fixed Version label on the title screen not being translatable (issue #2914).
    * Updated translations: British English, Chinese (Simplified), Czech, French,
      Galician, Italian, Polish, Scottish Gaelic, Slovak, Spanish, Ukrainian
  ### Lua API

src/gui/dialogs/title_screen.cpp

@@ -17,11 +17,10 @@
 #include "gui/dialogs/title_screen.hpp"
 
 #include "addon/manager_ui.hpp"
-#include "formatter.hpp"
+#include "formula/string_utils.hpp"
 #include "game_config.hpp"
 #include "game_config_manager.hpp"
 #include "game_launcher.hpp"
-#include "gettext.hpp"
 #include "gui/auxiliary/find_widget.hpp"
 #include "gui/auxiliary/tips.hpp"
 #include "gui/core/timer.hpp"
@@ -239,7 +238,7 @@ void title_screen::pre_show(window& win)
 	//
 	// Version string
 	//
-	const std::string version_string = formatter() << ("Version") << " " << game_config::revision;
+	const std::string& version_string = VGETTEXT("Version $version", {{ "version", game_config::revision }});
 
 	if(label* version_label = find_widget<label>(&win, "revision_number", false, false)) {
 		version_label->set_label(version_string);