libstdc++: Remove init_priority attribute for Init object [PR 98108]

This reverts commit cf4ed3b4.

libstdc++-v3/ChangeLog:

    PR libstdc++/98108
    * include/std/iostream (__ioinit): Remove init_priority attribute.

libstdc++-v3/include/std/iostream

@@ -70,16 +70,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #endif
   //@}
 
-#if __has_attribute(__init_priority__)
-# define _GLIBCXX_INIT_PRIO(N) __attribute__((__init_priority__(N)))
-#else
-# define _GLIBCXX_INIT_PRIO(N)
-#endif
-
   // For construction of filebuffers for cout, cin, cerr, clog et. al.
-  static ios_base::Init __ioinit _GLIBCXX_INIT_PRIO(90);
-
-#undef _GLIBCXX_INIT_PRIO
+  static ios_base::Init __ioinit;
 
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace