fix: remove input from column names

For https://gitlab.com/gitlab-org/modelops/ai-model-validation-and-research/ai-evaluation/evaluation-runner/-/issues/67

The dataset was previously uploaded with column headers prefixed by input_* which then caused and error where the evaluator couldn't find the proper input args. I updated the dataset in Langsmith here https://smith.langchain.com/public/04b79268-7c17-4674-ae3b-095fd19a8bce/d to have the proper args which should fix the error.