chore: Enable clang-tidy modernize checks (#6975)

Co-authored-by: Bart <11445373+bthomee@users.noreply.github.com>
Co-authored-by: Bart <bthomee@users.noreply.github.com>

src/test/jtx/impl/vault.cpp

@@ -14,9 +14,7 @@
 #include <optional>
 #include <tuple>
 
-namespace xrpl {
-namespace test {
-namespace jtx {
+namespace xrpl::test::jtx {
 
 std::tuple<Json::Value, Keylet>
 Vault::create(CreateArgs const& args) const
@@ -86,6 +84,4 @@ Vault::clawback(ClawbackArgs const& args)
     return jv;
 }
 
-}  // namespace jtx
-}  // namespace test
-}  // namespace xrpl
+}  // namespace xrpl::test::jtx