ci: fix Dockerfile.cuda: FromAsCasing: 'as' and 'FROM' keywords' casi…

…ng do not match (TabbyML#2629)

When docker build then log show:

```txt
 2 warnings found (use --debug to expand):
 - FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 9)
 - FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 49)
```