Replace deprecated std::random_shuffle by std::shuffle

This fixes the following clang-tidy warning:

    src/rssfeed.cpp:338:8: warning: 'random_shuffle<__gnu_cxx::__normal_iterator<std::shared_ptr<newsboat::RssItem> *, std::vector<std::shared_ptr<newsboat::RssItem>>>>' is deprecated: use 'std::shuffle' instead [clang-diagnostic-deprecated-declarations]
                    std::random_shuffle(items_.begin(), items_.end());
                         ^
    /usr/lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/stl_algo.h:4539:5: note: 'random_shuffle<__gnu_cxx::__normal_iterator<std::shared_ptr<newsboat::RssItem> *, std::vector<std::shared_ptr<newsboat::RssItem>>>>' has been explicitly marked deprecated here
        _GLIBCXX14_DEPRECATED_SUGGEST("std::shuffle")
        ^
    /usr/lib/gcc/x86_64-linux-gnu/12/../../../../include/x86_64-linux-gnu/c++/12/bits/c++config.h:112:45: note: expanded from macro '_GLIBCXX14_DEPRECATED_SUGGEST'
                                                ^
    /usr/lib/gcc/x86_64-linux-gnu/12/../../../../include/x86_64-linux-gnu/c++/12/bits/c++config.h:96:19: note: expanded from macro '_GLIBCXX_DEPRECATED_SUGGEST'
      __attribute__ ((__deprecated__ ("use '" ALT "' instead")))
                      ^

src/rssfeed.cpp

@@ -8,9 +8,10 @@
 #include <functional>
 #include <iostream>
 #include <langinfo.h>
+#include <random>
 #include <sstream>
-#include <sys/utsname.h>
 #include <string.h>
+#include <sys/utsname.h>
 #include <time.h>
 
 #include "cache.h"
@@ -335,7 +336,9 @@ void RssFeed::sort_unlocked(const ArticleSortStrategy& sort_strategy)
 		});
 		break;
 	case ArtSortMethod::RANDOM:
-		std::random_shuffle(items_.begin(), items_.end());
+		std::random_device rd;
+		std::default_random_engine rng(rd());
+		std::shuffle(items_.begin(), items_.end(), rng);
 		break;
 	}
 }