test/utils: remove a pointless .public_key call in issue_cert

PKey::EC#public_key works differently from other PKey types, making
TestUtils.issue_cert unusable for creating ECDSA certificates.
Actually, the #public_key does not have any effect on any other PKey
types. So just remove it.

Author: rhenium

test/utils.rb

@@ -67,7 +67,7 @@ def issue_cert(dn, key, serial, extensions, issuer, issuer_key,
     cert.serial = serial
     cert.subject = dn
     cert.issuer = issuer.subject
-    cert.public_key = key.public_key
+    cert.public_key = key
     now = Time.now
     cert.not_before = not_before || now - 3600
     cert.not_after = not_after || now + 3600