Comply with spec for permissions needed to delete a resource

Basically, until https://github.com/solid/web-access-control-spec/issues/47 gets discussed with a proper decision process, let's undo what was done in https://github.com/solid/node-solid-server/issues/729.

I'm not so fussed about the actual behaviour, I just want to start the process of documenting what we consider the spec (see also https://github.com/solid/solid-spec/issues/174), and on which points we are aware of differences between NSS and the spec.

Wherever such differences exist, if we think that NSS is right, then we should update the spec.
And if we think the spec is right (like in this case), we should (at least create a github issue to) fix NSS.

PS: If anyone is aware of any other points on which NSS is not spec-compliant, then let's create issues for each one of those. We can decide to willingly leave NSS broken, but at least we should have github issues that document how NSS is broken.

先閱讀連結的 web-access-control-spec issue 47、NSS issue 729 和 solid-spec issue 174，以比較刪除資源所需的權限要求。issue 中沒有指定檔案或測試；完成標準是記錄 NSS 與 spec 之間的差異並記錄決定，如果需要變更實作，則建立後續的 NSS issue。