test: remove qt byteswap compattests

These were added as part of #9366 to fix issues with Protobuf.

Now that we no-longer use Protobuf, there's no reason to maintain a
duplicate set of byteswap tests for qt.

src/test/bswap_tests.cpp

@@ -11,7 +11,6 @@ BOOST_FIXTURE_TEST_SUITE(bswap_tests, BasicTestingSetup)
 
 BOOST_AUTO_TEST_CASE(bswap_tests)
 {
-    // Sibling in bitcoin/src/qt/test/compattests.cpp
     uint16_t u1 = 0x1234;
     uint32_t u2 = 0x56789abc;
     uint64_t u3 = 0xdef0123456789abc;