Non ascii is fine for Pouta volumes

[jpcsc]

It seems like that non-ASCII characters for Pouta volumes are fine in the current openstack versions of Wallaby and Xena.

• https://csc-guide-preview.2.rahtiapp.fi/origin/non-ASCII-is-fine/cloud/pouta/persistent-volumes/

Removal of unnecessary README.txt

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[lvarin]

LGTM