tldextract used with a file url caches the file

1. Delete the cache if it exists (`~/.cache/python-tldextract/`)
2. Initialize and use tldextract with the list from a file: `import tldextract; tldextract.TLDExtract(suffix_list_urls=("file:///usr/share/publicsuffix/public_suffix_list.dat",))("debian.org")`
3. Notice that `~/.cache/python-tldextract/` is created or that tldextract logs a warning on read only systems

I think that it makes little sense to copy the specified file to cache. It does however create several issues:
1. On read only systems cache needs to be explicitly disabled to avoid warnings
2. More importantly, modifications in the suffix file don't immediately affect the results of tldextract leading to a lot of confusion