'Asia/Saigon' and 'Asia/Katmandu' are canonical even though they became obsolete in 1993

[jungshik]

Moved from ​ICU ticket 12044 .

​http://unicode.org/repos/cldr/tags/latest/common/bcp47/timezone.xml has the following:

<type name="mnuln" description="Ulaanbaatar (Ulan Bator), Mongolia" alias="Asia/Ulaanbaatar Asia/Ulan_Bator"/>
<type name="npktm" description="Kathmandu, Nepal" alias="Asia/Katmandu Asia/Kathmandu"/>
<type name="vnsgn" description="Ho Chi Minh City, Vietnam" alias="Asia/Saigon Asia/Ho_Chi_Minh"/>

If the first in alias field is canonical, for the two timezones shown above, canonical names in CLDR are 'outdated'.

I'm aware that CLDR canonical timezone ids are to be stable and don't change despite changes in IANA tz database, but for the above two zones, 'Asia/Ho_Chi_Minh' and 'Asia/Kathmandu' (with 'h') have been canonical since 1993 (probably before the CLDR started) if what's in the 'backwards' file of ​https://www.iana.org/time-zones is to be believed.

I'm not sure what can be done for them.