`@headitem` distorts vertical spacing

[Werner LEMBERG]

[texinfo version 2022-09-01.06]


Consider the following example.

```
\input texinfo.tex

foo

@multitable {blubb} {bla}
@item blubb @tab bla
@item blubb @tab bla
@end multitable

bar

@multitable {blubb} {bla}
@headitem blubb @tab bla
@item     blubb @tab bla
@end multitable

baz

@bye
```

As can be seen, `@headitem` inserts extra vertical space, which looks
ugly.