Add future to Python requirements

- Add `future` to the requirements.txt, set to >=1.0.0. 1.0.0 adds
  support for Python 3.12.

Change-Id: Ib4820b06408fa6af53aed29d3af68c3da176177d
Bypass-Presubmit-Reason: No presubmits configured, topic presubmit passed.

python-requirements.txt

diff --git a/python-requirements.txt b/python-requirements.txt
index 162a3c1..2868bd5 100644
--- a/python-requirements.txt
+++ b/python-requirements.txt
@@ -27,6 +27,7 @@
 flatbuffers>=23.5.26
 
 filecheck
+future>=1.0.0
 hjson
 jsonschema
 lit