[cpp] don't disable unicode support in sys tests #8090

tests/sys/compile-cpp.hxml

@@ -1,16 +1,13 @@
 compile-each.hxml
---define disable-unicode-strings
 --main Main
 -cpp bin/cpp
 
 --next
 compile-each.hxml
---define disable-unicode-strings
 --main TestArguments
 -cpp bin/cpp
 
 --next
 compile-each.hxml
---define disable-unicode-strings
 --main ExitCode
 -cpp bin/cpp