Revert "[conda] Skip sympy for 3.12"

This reverts commit 88457a1.
As sympy has been updated to 1.12 and it now supports Python-3.12

Author: malfet

conda/pytorch-nightly/meta.yaml

@@ -49,7 +49,7 @@ requirements:
     # Before a decent fix, force llvm-openmp version <16.
     - llvm-openmp <16 # [linux]
     - typing_extensions
-    - sympy # [py < 312]
+    - sympy
     - filelock
     - networkx
     - jinja2