boehmgc: Remove unused code from patch

boehmgc-coroutine-sp-fallback.diff

@@ -1,5 +1,5 @@
 diff --git a/pthread_stop_world.c b/pthread_stop_world.c
-index 1cee6a0b..8977b0dd 100644
+index 1cee6a0b..46c3acd9 100644
 --- a/pthread_stop_world.c
 +++ b/pthread_stop_world.c
 @@ -674,6 +674,8 @@ GC_INNER void GC_push_all_stacks(void)
@@ -11,7 +11,7 @@ index 1cee6a0b..8977b0dd 100644
  
      if (!EXPECT(GC_thr_initialized, TRUE))
        GC_thr_init();
-@@ -723,6 +725,30 @@ GC_INNER void GC_push_all_stacks(void)
+@@ -723,6 +725,28 @@ GC_INNER void GC_push_all_stacks(void)
            hi = p->altstack + p->altstack_size;
            /* FIXME: Need to scan the normal stack too, but how ? */
            /* FIXME: Assume stack grows down */
@@ -35,9 +35,7 @@ index 1cee6a0b..8977b0dd 100644
 +              lo = hi - stack_limit;
 +            }
 +          #else
-+            if (lo < hi || lo >= hi + stack_limit) { // sp outside stack
-+              lo = hi + stack_limit;
-+            }
++          #error "STACK_GROWS_UP not supported in boost_coroutine2 (as of june 2021), so we don't support it in Nix."
 +          #endif
          }
          GC_push_all_stack_sections(lo, hi, traced_stack_sect);