1) Got rid of useless call to `cat`, much better to simply use sed with
file as argument.
2) Got rid of `sort -u`. There is no need to sort the list.
Additionally, the list `pyenv.d/rehash/conda.d/default.list` only has
unique entries, and even if you have duplicate entries, the function
will still work. --> No need for sort nor unique.
3) Further improvement is simple, save a cached
cleaned-list-v1.0 in `conda.d` and simple read from that file instead of
doing `sed`, which must be a more expensive operation than simply
reading from file.