Revert broken "deque.hpp: Improve shrink implementation"

This reverts commit daed60ee.

rt/include/typon/fundamental/ring_buffer.hpp

@@ -69,24 +69,7 @@ namespace typon::fdt::lock_free
 
     ring_buffer * shrink(u64 start, u64 end) noexcept
     {
-      ring_buffer * last = nullptr;
-      ring_buffer * next = this;
-      u64 size = end - start;
-      while (auto buff = next->_next)
-      {
-        if (buff->capacity() < size * 4)
-        {
-          break;
-        }
-        last = next;
-        next = buff;
-      }
-      if (!last)
-      {
-        return nullptr;
-      }
-      last->_next = nullptr;
-      return fill(next, start, end);
+      return fill(std::exchange(_next, nullptr), start, end);
     }
   };