Fix a lot of man7 links to be more specific.

Bug: https://github.com/android/ndk/issues/2113
Change-Id: Ifc3add91c39422985c63e895dc32443b8f736c9d
diff --git a/libc/include/time.h b/libc/include/time.h
index 6c9b761..777e648 100644
--- a/libc/include/time.h
+++ b/libc/include/time.h
@@ -281,7 +281,7 @@
 char* _Nullable ctime(const time_t* _Nonnull __t);
 
 /**
- * [ctime_r(3)](https://man7.org/linux/man-pages/man3/ctime.3p.html) formats
+ * [ctime_r(3)](https://man7.org/linux/man-pages/man3/ctime_r.3p.html) formats
  * the time `tm` as a string in the given buffer `buf`.
  *
  * Returns a pointer to a string on success, and returns NULL on failure.