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/app/GRPCServerTLS_test.cpp

@@ -334,8 +334,7 @@ private:
 
 }  // namespace
 
-namespace xrpl {
-namespace test {
+namespace xrpl::test {
 /**
  * Helper function to make a simple gRPC call to test connectivity.
  * Returns true if the call succeeded, false otherwise.
@@ -847,5 +846,4 @@ public:
 
 BEAST_DEFINE_TESTSUITE(GRPCServerTLS, app, xrpl);
 
-}  // namespace test
-}  // namespace xrpl
+}  // namespace xrpl::test