Help: Fix memory leak given ambiguous man page title on command line

Given a command line with an ambiguous man page title, such as `$ Help
uname`, Help would find and try to open all matching pages, leading to
bad behavior such as a memory leak, flickering scrollbars, and
eventually a crash due to OOM. This commit fixes the issue by making
Help only open one page on startup.

Userland/Applications/Help/main.cpp

@@ -331,6 +331,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
                     history.push(path);
                     open_page(path);
                     set_start_page = true;
+                    break;
                 }
             }