Fix doc nightly doc CI (#3611)

mthrok · mthrok · commit 420d9ac38ffb · 2023-09-19T15:28:19.000-04:00
Some changes at matplotlib 3.8.0 rejects torch.Tensor passed to `plot` function.
diff --git a/docs/requirements.txt b/docs/requirements.txt
@@ -1,5 +1,5 @@
 Jinja2<3.1.0
-matplotlib
+matplotlib<=3.8
 pyparsing<3,>=2.0.2
 
 # C++ docs
