Fix `--cache-file` implementation

[Bassem Dghaidi]

When running this command, the cache file is not found

gh stars --user 'link-' --cache-file '/tmp/.cache' --find 'es6' --debug

INFO: 2023/05/13 17:00:53 root.go:91: Debug mode is enabled
INFO: 2023/05/13 17:00:53 root.go:92: Parameters provided  --user link- 
--cache-file /tmp/.cache --find es6 --debug
INFO: 2023/05/13 17:00:53 root.go:239: Attempting to fetch the total number of 
starred repos for user link-
INFO: 2023/05/13 17:00:53 root.go:269: CacheKey generated: 
d856442b086a3c61b6593f22bf91804c91cbb53bfb585aa9217550f8c0271a5c
INFO: 2023/05/13 17:00:53 root.go:282: Cache file provided as input: 
/tmp/.cache
ERROR: 2023/05/13 17:00:53 root.go:106: Not able to get starred reposopen 
/tmp/.cache: no such file or directory

[Bassem Dghaidi]

This is a non issue, file should exist and be writable already. The tool should not create a file that's passed as a parameter.