Revert "fix: provides are not recognized for erase command. (RhBug:1087063)"

This reverts commit a4ca8bff5f99adbbf76fa13210c885e19dca6620.

This feature makes CLI commands inconsistent (the others look for providse
too). Also: 'dnf install syslog && dnf erase syslog' fails with nothing to
remove in the second step. Lastly, the Base.remove() API call still does
look for provides of course, so this would introduce further discrepancy
between CLI and API.
cosmetics: leave around the good things from 660c3e5 (documentation, UT).