Fix another clang-tidy warning

Author: greg7mdp

parallel_hashmap/phmap.h

@@ -1193,7 +1193,7 @@ class raw_hash_set
         // Hash, equality and allocator are copied instead of moved because
         // `that` must be left valid. If Hash is std::function<Key>, moving it
         // would create a nullptr functor that cannot be called.
-        settings_(that.settings_) {
+        settings_(std::move(that.settings_)) {
         // growth_left was copied above, reset the one from `that`.
         that.growth_left() = 0;
     }