Fix suppressing news nag after reading the news (#3817)

The news nag suppression regressed again in 5c67d22. That commit
intended to remove the sponsorship outro from the news, but also removed
the bookkeeping that marks the news as read. This commit reverts that
part back to its previous state.

src/commands/CmdNews.cpp

@@ -588,6 +588,11 @@ int CmdNews::execute(std::string& output) {
   }
   wait_for_enter();
 
+  // Set a mark in the config to remember which version's release notes were displayed
+  if (news_version < current_version) {
+    CmdConfig::setConfigVariable("news.version", std::string(current_version), false);
+  }
+
   return 0;
 }