`d` in diff-mode + visual selection does not kill text

[Hi-Angel]

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Before trying to send a PR to fix that I decided to create this issue to discuss.

The problem case: I was editing a diff file. I have selected a large part of the diff that covers multiple files and pressed d to remove it. Then I saved and applied it. Now, can you imaging my surprise when I found that literally nothing has changed. The files I removed were still there, in git. Upon closer inspection turns out that evil-collection has bound this key to some mode-specific action diff-hunk-kill

I see 2 problems with that:

1.That seems to kind of beat the purpose of the plugin because from my understanding the plugin is trying to help with various annoying modes that override common Evil keybindings. But in this case it is the plugin that overrides it. 2. Even setting 1 aside, why d in visual mode? It is more confusing than it is helpful, because visual mode implies you've selected some region and so diff-hunk-kill should do the action over the region. Which diff-hunk-kill does not support.

Should the hotkey perhaps be removed?

[Hi-Angel]

CC: @Ambrevar the commit author