owncloud705: remove vulnerable version

cc #30959

pkgs/servers/owncloud/default.nix

···
 
 in {
 
-  owncloud705 = common {
-    versiona = "7.0.5";
-    sha256 = "1j21b7ljvbhni9l0b1cpzlhsjy36scyas1l1j222mqdg2srfsi9y";
-  };
-
   owncloud70 = common {
     versiona = "7.0.15";
     sha256 = "1b2a0fccxlkqyyzsymx7qw8qbhsks3i6h1ybvxv8nn8hgw33nqv7";