Cap psutil at the major that is actually tested

The previous commit set <8, which still allowed psutil 6 and 7 through —
both untested here, which is the exact thing the ceilings exist to stop.
The machine that tests this runs 5.9.4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: ColinGPT9

requirements.txt

@@ -34,5 +34,7 @@ google-api-python-client>=2.100.0,<3
 google-auth-oauthlib>=1.1.0,<2
 # 0.x: a minor bump here can break, so the ceiling is tighter than the rest.
 curl_cffi>=0.7.0,<0.16
-psutil>=5.9.0,<8
+# <6, not <8: 6 and 7 exist but have never run here. Same rule as the rest —
+# the ceiling sits at the major that is actually tested.
+psutil>=5.9.0,<6
 nvidia-ml-py>=12.0.0,<14