[sympy] fix ValueRanges.pow error when b.lower is float (#95151)
Summary:
fix `TypeError: 'Float' object cannot be interpreted as an integer` for `ValueRanges.pow(a, b)` when `not a.is_singleton() and b.is_singleton() and not isinstance(b.lower, int)`
this is breaking `cuda11.7-py3.10-gcc7-sm86 / test (inductor_timm, 1, 2, linux.g5.4xlarge.nvidia.gpu)`
{F878635541}
Test Plan: sandcastle + CI
Differential Revision: D43430385
Pull Request resolved: https://github.com/pytorch/pytorch/pull/95151
Approved by: https://github.com/Skylion007
