examples/64: relax exact CC 8.9 gate to inclusive check

[SAR2652]

Fixes #3524

Example 64 gated on compute capability exactly 8.9, rejecting newer
architectures despite the kernels compiling and running correctly. This
uses the inclusive form already present in example 58
(major < 8 || (major == 8 && minor < 9)), and updates the error
message to match.

Verified on sm_120a, CUDA 13.0, CUTLASS 4.8.0:

cmake .. -DCUTLASS_NVCC_ARCHS=120a
make 64_ada_fp8_gemm_grouped

Grouped GEMM (CUTLASS) with mode kDeviceOnly:
    9300 total threadblock tiles.
    Grouped Runtime: 6.32188 ms
    Grouped  GFLOPs: 54070.7
Passed