util/tuple_utils.hh: avoid redundant move
util/tuple_utils.hh: avoid redundant move

per the resolution of https://wg21.link/cwg1148 , a move should be used
in this case: the parameter is an lvalue, but it's about to be
destroyed, so the compiler should consider it as an rvalue.

this change silences the warnings from GCC-10 and Clang-9 with
-Wredundant-move, like:

../src/seastar/include/seastar/util/tuple_utils.hh:34:23: warning:
redundant move in return statement [-Wredundant-move]
   34 |     return std::move(t);
      |                       ^
../src/seastar/include/seastar/util/tuple_utils.hh:34:23: note: remove
‘std::move’ call

and

error: redundant move in return statement [-Werror,-Wredundant-move]
  return std::move(t); // move used implicitly
         ^

Signed-off-by: Kefu Chai <a4b264ee037c625052534d60505bfd0db4776ac4@redhat.com>
Message-Id: <b50c2aa9c2b4302469bb12fa9ee3ca70859ad30c@gmail.com>

syuu1228/seastar,scylladb/seastar,avikivity/seastar,dreamsxin/seastar,scylladb/seastar,cloudius-systems/seastar,avikivity/seastar,scylladb/seastar,syuu1228/seastar,cloudius-systems/seastar,cloudius-systems/seastar,syuu1228/seastar,dreamsxin/seastar,avikivity/seastar,dreamsxin/seastar