tests: hide warning on clang

[henryiii]

Description

Hide a warning in our tests on clang.

Warnings look like this:

D:/a/pybind11/pybind11/tests/test_constants_and_functions.cpp:59:15: warning: dynamic exception specifications are deprecated [-Wdeprecated-dynamic-exception-spec]
   59 | int f4(int x) throw() { return x + 4; } // Deprecated equivalent to noexcept(true)
      |               ^~~~~~~
D:/a/pybind11/pybind11/tests/test_constants_and_functions.cpp:59:15: note: use 'noexcept' instead
   59 | int f4(int x) throw() { return x + 4; } // Deprecated equivalent to noexcept(true)
      |               ^~~~~~~
      |               noexcept
D:/a/pybind11/pybind11/tests/test_constants_and_functions.cpp:72:19: warning: dynamic exception specifications are deprecated [-Wdeprecated-dynamic-exception-spec]
   72 |     int m7(int x) throw() { return x - 7; }
      |                   ^~~~~~~
D:/a/pybind11/pybind11/tests/test_constants_and_functions.cpp:72:19: note: use 'noexcept' instead
   72 |     int m7(int x) throw() { return x - 7; }
      |                   ^~~~~~~
      |                   noexcept
D:/a/pybind11/pybind11/tests/test_constants_and_functions.cpp:74:25: warning: dynamic exception specifications are deprecated [-Wdeprecated-dynamic-exception-spec]
   74 |     int m8(int x) const throw() { return x - 8; }
      |                         ^~~~~~~
D:/a/pybind11/pybind11/tests/test_constants_and_functions.cpp:74:25: note: use 'noexcept' instead
   74 |     int m8(int x) const throw() { return x - 8; }
      |                         ^~~~~~~
      |                         noexcept

3 warnings generated.

[rwgk]

Do you still have the warning handy (the warning that's being suppressed with this PR)?

Copy-pasting it into the PR description might be a super easy way to be helpful (Google searches).

Not a big deal, but usually that's what I do.