scripts: remove erroneous file that breaks git clone on Windows

scripts: remove erroneous file that breaks git clone on Windows

This file was created by mistake in recent ed7667188 (9p: remove
'proxy' filesystem backend driver).

When cloning the repository using native git for windows, we see this:
Error: error: invalid path 'scripts/meson-buildoptions.'
Error: The process 'C:\Program Files\Git\bin\git.exe' failed with exit code 128
Link: https://lore.kernel.org/r/20241023073914.895438-1-pierrick.bouvier@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>