remove .R files with zero coverage

[adw96]

Overall we are doing really great on code coverage (>74%) 🥳 There are a few files which have zero code coverage and I would love them to be removed if they have been deprecated. Here's the list

• R/calculate_U.R: 0.00%
• R/crossfit_U.R: 0.00%
• R/dfs_to_derivs.R: 0.00%
• R/dfs_to_mean.R: 0.00%
• R/fit_simple_model.R: 0.00%
• R/get_gmm_inv_weights.R: 0.00%
• R/mu_d_beta_faster.R: 0.00%
• R/numerical_jacobian.R: 0.00%
• R/push_row.R: 0.00%
• R/refit_model.R: 0.00%
• R/safe_multiply.R: 0.00%
• R/simulate_simple_data.R: 0.00%
• R/universal_test.R: 0.00%

You can run git rm R/[name of the file] to delete a file and remove it from git tracking.

Thanks, David!