contrib/tzdata: import tzdata 2023c

Changes: https://github.com/eggert/tz/blob/2023c/NEWS

The tzdata 2023c release reverts all changes made in 2023b other than
commentary, as that appears to be the best of a bad set of short-notice
choices for modeling this week's daylight saving chaos in Lebanon.

(cherry picked from commit 9fbeeb6e38310b4f42a14c4b043bbee82c5e4752)