Remove unused RTS function 'unmark'

rts/sm/Compact.h

@@ -25,16 +25,6 @@ mark(StgPtr p, bdescr *bd)
     *bitmap_word |= bit_mask;
 }
 
-INLINE_HEADER void
-unmark(StgPtr p, bdescr *bd)
-{
-    uint32_t offset_within_block = p - bd->start; // in words
-    StgPtr bitmap_word = (StgPtr)bd->u.bitmap +
-        (offset_within_block / BITS_IN(W_));
-    StgWord bit_mask = (StgWord)1 << (offset_within_block & (BITS_IN(W_) - 1));
-    *bitmap_word &= ~bit_mask;
-}
-
 INLINE_HEADER StgWord
 is_marked(StgPtr p, bdescr *bd)
 {