Revert "rts: Ensure that the_gc_thread is aligned"

This reverts commit 87a79e39.

rts/sm/GC.c

@@ -128,11 +128,7 @@ uint32_t mutlist_MUTVARS,
 gc_thread **gc_threads = NULL;
 
 #if !defined(THREADED_RTS)
-/* Use conservative alignment since we will cast this to a gc_thread and
- * consequently the compiler may assume it is aligned. See #15482.
- */
-StgWord8 the_gc_thread[sizeof(gc_thread) + 64 * sizeof(gen_workspace)]
-    __attribute__((aligned(sizeof(W_))));
+StgWord8 the_gc_thread[sizeof(gc_thread) + 64 * sizeof(gen_workspace)];
 #endif
 
 // Number of threads running in *this* GC.  Affects how many