Add noexcept as std::shared_ptr::reset() is noexcept (#576)

Author: tetsuhaut

include/stlab/concurrency/future.hpp

@@ -828,7 +828,7 @@ class STLAB_NODISCARD() future<T, enable_if_copyable<void_to_monostate_t<T>>> {
         self._detach(std::move(*this), std::forward<F>(f));
     }
 
-    void reset() { _p.reset(); }
+    void reset() noexcept { _p.reset(); }
 
     [[nodiscard]] auto is_ready() const& -> bool { return _p && _p->is_ready(); }
 
@@ -945,7 +945,7 @@ class STLAB_NODISCARD() future<T, enable_if_not_copyable<void_to_monostate_t<T>>
         self._detach(std::move(*this), std::forward<F>(f));
     }
 
-    void reset() { _p.reset(); }
+    void reset() noexcept { _p.reset(); }
 
     [[nodiscard]] auto is_ready() const& -> bool { return _p && _p->is_ready(); }