This mostly fixes some wrong indents or replaces some stray tab indents.
I excluded alignment on purpose, because we have a whole bunch of code
that goes like
```fish
complete -c foo -n 'some-condition' -l someoption
complete -c foo -n 'some-longer-condition' -l someotheroption
```
and changing it seems like a larger thing and would include more
thrashing.
See #3622.