Minor typo in the help sections - 'previous' vs 'previous-year'

[TheAnalogyGuy]

https://github.com/iridakos/stup/blob/955e24cdbceb429f95b4ee0df4cdb609e3f2e1b7/stup#L1671 Should be: printf "\n%15s %s" "previous-year" "Alias to list the notes of previous-year"

https://github.com/iridakos/stup/blob/955e24cdbceb429f95b4ee0df4cdb609e3f2e1b7/stup#L1711 Should be printf "\n%15s %s" "previous-year" "Alias to search the notes of previous-year"

Example when running command based on current help: Incorrect:

$ stup search 'foo' previous
Error: Unknown command "previous"

Correct:

$ stup search 'foo' previous-year
Searching for term 'foo' in all categories.
Searching notes from Friday January 01, 2021 to Friday December 31, 2021
Nothing found.