20.5 generates enum redirector warnings for old assets

[moppius]

If people upgrade to latest 20.5 straight from 19.5 without having gone through the intermediate HoudiniEngine version, any old assets will generate warnings due to invalid enum redirects.

• Some values of EHoudiniInputType were deprecated 9 months ago in b3ed09b
  • Enum redirectors for these deprecated values were added at the same time
• Last month, the deprecated enum values were removed for Houdini 20 in 294de41
  • The enum redirectors were not removed, so now this generates a warning for redirecting to an invalid value...

Presumably these redirectors should be removed, or set to redirect to whatever the most reasonable current value should be.

Also it would mean that anyone who has assets saved which pointed to the old _DEPRECATED values will now lose their data.