Fix tutorial to accomodate new amino acid alignments data

[mcjmigdal]

After the external data update some of the sections in the tutorial are failing

eg

devtools::load_all()
dat_pheno <-
  read.table(
  file = system.file("extdata", "MiDAS_tut_pheno.txt", package = "midasHLA"),
  header = TRUE
  )
dat_HLA <-
  readHlaCalls(
  file = system.file("extdata", "MiDAS_tut_HLA.txt", package = "midasHLA"),
  resolution = 4
  )
HLA_AA <- prepareMiDAS(
  hla_calls = dat_HLA,
  colData = dat_pheno,
  experiment = "hla_aa"
)
HLA_AA[["hla_aa"]] %>%
  assay() %>%
  t() %>%
  as.data.frame() %>%
  select(starts_with("B_110_")) %>%
  head()

[mcjmigdal]

Blocked by #32