Revise README checkpoint link texts from 50B to 51B

Revise checkpoint link texts: 50B --> 51B

Author: baileykuehl

README.md

@@ -112,9 +112,9 @@ For the 1B model, we have trained three times with different data order on 50B h
 
 |                        | Checkpoint                                                                                                                          | Training config                                                                        | WandB       |
 |------------------------|-------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------|-------------|
-| random seed 42069         | [stage2-ingredient1-step23852-tokens50B](https://huggingface.co/allenai/OLMo-2-0425-1B/tree/stage2-ingredient1-step23852-tokens51B) | [OLMo2-1B-stage2-seed42069.yaml](configs/official-0425/OLMo2-1B-stage2-seed42069.yaml)       | [wandb.ai/OLMo2-1B](https://api.wandb.ai/links/ai2-llm/izdtrtu0) |
-| random seed 666      | [stage2-ingredient2-step23852-tokens50B](https://huggingface.co/allenai/OLMo-2-0425-1B/tree/stage2-ingredient2-step23852-tokens51B) | [OLMo2-1B-stage2-seed666.yaml](configs/official-0425/OLMo2-1B-stage2-seed666.yaml) | [wandb.ai/OLMo2-1B](https://api.wandb.ai/links/ai2-llm/izdtrtu0) |
-| random seed 42  (main)      | [stage2-ingredient3-step23852-tokens50B](https://huggingface.co/allenai/OLMo-2-0425-1B/tree/stage2-ingredient3-step23852-tokens51B) | [OLMo2-1B-stage2-seed42.yaml](configs/official-0425/OLMo2-1B-stage2-seed42.yaml)     | [wandb.ai/OLMo2-1B](https://api.wandb.ai/links/ai2-llm/izdtrtu0) |
+| random seed 42069         | [stage2-ingredient1-step23852-tokens51B](https://huggingface.co/allenai/OLMo-2-0425-1B/tree/stage2-ingredient1-step23852-tokens51B) | [OLMo2-1B-stage2-seed42069.yaml](configs/official-0425/OLMo2-1B-stage2-seed42069.yaml)       | [wandb.ai/OLMo2-1B](https://api.wandb.ai/links/ai2-llm/izdtrtu0) |
+| random seed 666      | [stage2-ingredient2-step23852-tokens51B](https://huggingface.co/allenai/OLMo-2-0425-1B/tree/stage2-ingredient2-step23852-tokens51B) | [OLMo2-1B-stage2-seed666.yaml](configs/official-0425/OLMo2-1B-stage2-seed666.yaml) | [wandb.ai/OLMo2-1B](https://api.wandb.ai/links/ai2-llm/izdtrtu0) |
+| random seed 42  (main)      | [stage2-ingredient3-step23852-tokens51B](https://huggingface.co/allenai/OLMo-2-0425-1B/tree/stage2-ingredient3-step23852-tokens51B) | [OLMo2-1B-stage2-seed42.yaml](configs/official-0425/OLMo2-1B-stage2-seed42.yaml)     | [wandb.ai/OLMo2-1B](https://api.wandb.ai/links/ai2-llm/izdtrtu0) |
 
 
 ### Stage 2 for the 7B