CLI autocompletion should not print equals sign `=`

This is an issue of style.

Steps to reproduce:
```
$ dnf repoquery --whatp<TAB><TAB>
...
$ dnf repoquery --whatprovides=
```
I don't know any other CLI tool that autocompletes equals signs instead of spaces. Moreover, `rpm` itself autocompletes spaces as does `dnf4`:
```
$ rpm -q --whatp<TAB><TAB>
...
$ rpm -q --whatprovides<SPACE>
```