update_sigma_list: Update the sigma parameter for each cluster
In jewelltaylor/fdcvi:

Update the sigma parameter for each cluster

update_sigma_list(
  cluster_data,
  phi_matrix,
  number_of_clusters,
  A_vector,
  R_vector,
  probability_matrix,
  sequence,
  nbasis
)

`cluster_data`	The matrix containing rows corresponding the curves
`phi_matrix`	A matrix of the coffecient vectors for each cluster, phi_k, of the basis matrix B
`number_of_clusters`	The total number of clusters
`A_vector`	A vector
`R_vector`	A vector
`probability_matrix`	A matrix in which the rows represent the probabilities that the curve is in each of the clusters
`sequence`	The sequence used to generate the clusters
`nbasis`	The number of basis functions