libressl_2_8: remove, not maintained anymore

Stable LibreSSL releases are supported one year after their OpenBSD release.
OpenBSD 6.4 with this branch was released on 2018-10-18.

pkgs/development/libraries/libressl/default.nix

@@ -64,11 +64,6 @@ let
 
 in {
 
-  libressl_2_8 = generic {
-    version = "2.8.3";
-    sha256 = "0xw4z4z6m7lyf1r4m2w2w1k7as791c04ygnfk4d7d0ki0h9hnr4v";
-  };
-
   libressl_2_9 = generic {
     version = "2.9.2";
     sha256 = "1m6mz515dcbrbnyz8hrpdfjzdmj1c15vbgnqxdxb89g3z9kq3iy4";

pkgs/top-level/all-packages.nix

@@ -13099,7 +13099,6 @@ in
   openvdb = callPackage ../development/libraries/openvdb {};
 
   inherit (callPackages ../development/libraries/libressl { })
-    libressl_2_8
     libressl_2_9
     libressl_3_0;