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/seq.cpp

@@ -5,9 +5,7 @@
 
 #include <xrpl/protocol/jss.h>
 
-namespace xrpl {
-namespace test {
-namespace jtx {
+namespace xrpl::test::jtx {
 
 void
 seq::operator()(Env&, JTx& jt) const
@@ -19,6 +17,4 @@ seq::operator()(Env&, JTx& jt) const
         jt[jss::Sequence] = *num_;
 }
 
-}  // namespace jtx
-}  // namespace test
-}  // namespace xrpl
+}  // namespace xrpl::test::jtx