Fixes the way seed was set in the benchmark_non_rl script (#3741)

# Description

When seed was added to the benchmark_non_rl.py script, it was mistakenly
trying to read from simulation config, which doesn't exist. We can set
seed directly from the cli arguments since it's ok to be None if it's
not specified.


## Type of change

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- Bug fix (non-breaking change which fixes an issue)


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- [ ] I have added tests that prove my fix is effective or that my
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Author: kellyguo11

scripts/benchmarks/benchmark_non_rl.py

@@ -113,7 +113,7 @@ def main(env_cfg: ManagerBasedRLEnvCfg | DirectRLEnvCfg | DirectMARLEnvCfg, agen
     # override configurations with non-hydra CLI arguments
     env_cfg.scene.num_envs = args_cli.num_envs if args_cli.num_envs is not None else env_cfg.scene.num_envs
     env_cfg.sim.device = args_cli.device if args_cli.device is not None else env_cfg.sim.device
-    env_cfg.seed = args_cli.seed if args_cli.seed is not None else env_cfg.sim.seed
+    env_cfg.seed = args_cli.seed
 
     # process distributed
     world_size = 1