Revert "build: work around issue with Boost <= 1.80 and Clang >= 18"

This reverts commit cd062d6.

Author: MarcoFalke

src/txmempool.h

@@ -23,17 +23,7 @@
 #include <util/result.h>
 #include <util/feefrac.h>
 
-// This works around a bug in Boost <= 1.80.0 when using Clang >=18.
-// See https://github.com/bitcoin/bitcoin/issues/30751.
-#if defined(__clang__)
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wenum-constexpr-conversion"
-#endif
 #include <boost/multi_index/hashed_index.hpp>
-#if defined(__clang__)
-#pragma clang diagnostic pop
-#endif
-
 #include <boost/multi_index/identity.hpp>
 #include <boost/multi_index/indexed_by.hpp>
 #include <boost/multi_index/ordered_index.hpp>