bsdinstall: restore time selection screen

Apparently new dialog does not like the height of 2 for the
timebox widget, use 0 (minimum size) instead.

Do the same for calendar widget as it does not change the
appearance and to prevent possible future surprises.

Reviewed by:	bapt
Differential Revision:	https://reviews.freebsd.org/D29720

usr.sbin/bsdinstall/scripts/time

@@ -42,7 +42,7 @@ DATE=$(dialog --backtitle 'FreeBSD Installer' \
 	--cancel-label 'Skip' \
 	--defaultno \
 	--date-format '%Y%m%d%H%M.%S' \
-	--calendar '' 2 40 \
+	--calendar '' 0 40 \
 2>&1 1>&3) && date $DATE
 exec 3>&-
 
@@ -54,7 +54,7 @@ TIME=$(dialog --backtitle 'FreeBSD Installer' \
 	--cancel-label 'Skip' \
 	--defaultno \
 	--time-format '%H%M.%S' \
-	--timebox '' 2 40 \
+	--timebox '' 0 40 \
 2>&1 1>&3) && date $TIME
 exec 3>&-