Disable a dataflow fuzz test after "Have REQUIRES support the target triple"

See: https://lab.llvm.org/buildbot/#/builders/75/builds/8095/steps/8/logs/stdio

which shows:
unsupported option '-fsanitize=dataflow' for target 'i386-unknown-linux-gnu'

The other dataflow tests in the same directory were already disabled,
so I think it's fine to disable this one as well.