security/easy-rsa: sed \s -> :space:

Fix https://github.com/OpenVPN/easy-rsa/issues/714

Patch suggested (needed to be integrated) and
Reported by: topical@gmx.net
PR: 266726
MFH: 2022Q4

(cherry picked from commit 5d062d5c18a1de48b8c30bf69929e1e3cb37679f)