[libc] add ctime and ctime_r to docs (llvm#156216)

I noticed that I forgot to add `ctime` and `ctime_r` to docs in
llvm#107285. This is a simple patch
to add it.

Author: zimirza

libc/docs/headers/time.rst

@@ -73,9 +73,9 @@ Implementation Status
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
 | clock_settime       |         |         |         |                 |         |         |         |         |         |         |         |         |         |
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
-| ctime               |         |         |         |                 |         |         |         |         |         |         |         |         |         |
+| ctime               | |check| | |check| |         |     |check|     |         |         |         |         |         |         |         |         |         |
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
-| ctime_r             |         |         |         |                 |         |         |         |         |         |         |         |         |         |
+| ctime_r             | |check| | |check| |         |     |check|     |         |         |         |         |         |         |         |         |         |
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
 | difftime            | |check| | |check| |         |     |check|     |         |         |         |         |         |         |         |         |         |
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+