function dedupeStops(prefix: string, suffix: string): string {
  // We can naively grab the last "character" (a general Unicode "no-no") from
  // our string because we know our set of stops we test against have no
  // diacritics nor lie outside the BMP
  return isRedundant(prefix[prefix.length - 1], suffix) ? '' : suffix;
}
If suffix is redundant with prefix (as determined by the redundancy map),
return the empty string, otherwise return suffix.