Fix DLRMv3 fbgemm_gpu loading with hardcoded Bazel paths

[ssam18]

Problem

The DLRMv3 harness was using hardcoded Bazel build paths specific to Meta's internal build system:

torch.ops.load_library("//deeplearning/fbgemm/fbgemm_gpu:sparse_ops")
torch.ops.load_library("//deeplearning/fbgemm/fbgemm_gpu:sparse_ops_cpu")

This caused failures when running outside that environment:

FAILED to load sparse_ops_cpu in position: Could not load this library: /deeplearning/fbgemm/fbgemm_gpu:sparse_ops
FAILED to load sparse_ops_cpu in jagged: Could not load this library: /deeplearning/fbgemm/fbgemm_gpu:sparse_ops
FAILED to load sparse_ops_cpu in jagged tensors: Could not load this library: /deeplearning/fbgemm/fbgemm_gpu:sparse_ops
FAILED to load sparse_ops_cpu in hstu attention: Could not load this library: /deeplearning/fbgemm/fbgemm_gpu:sparse_ops

Fixes #2429

[github-actions]

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