Fix a couple typos in new submitter policy (#1135)

Author: dylanhmorris

model-output/README.md

@@ -288,13 +288,13 @@ Teams wishing to contribute a non-designated baseline model to the Hub may reque
 - The model is non-designated
 - Its status as a retrospective baseline is declared prominently in the model metadata
 
-## Policy on new contributors (on GitHub) of an existing model
+## Policy on new forecast submitters for existing models
 
-To ensure submissions for existing models are made by authorized individuals, we that submitters be listed in the model's [metadata YAML file](../model-metadata/README.md) as `designated_github_users` and/or as `model_contributors`. 
+To ensure submissions for existing models are made by authorized individuals, we require that submitters be listed in the model's [metadata YAML file](../model-metadata/README.md) as `designated_github_users` and/or as `model_contributors`. 
 
 To add one or more new authorized submitter(s) for an existing model, a currently authorized submitter should make a PR changing the model's metadata YAML file. Alternatively, a new submitter can themself open a PR changing the metadata, but a currently authorized submitter must endorse the change via a PR comment before it can be approved and merged.
 
 We strongly encourage adding all submitters as `designated_github_users`, as this allows for submission PRs that pass validation to be automerged without manual review.
 
 ## Evaluation criteria
-Forecasts will be evaluated using a variety of metrics, including the weighted interval score (WIS).
+Forecasts will be evaluated using a variety of metrics, including the weighted interval score (WIS).