Update homepage attributes: http -> https

Homepage link "http://.../" is a permanent redirect to "https://.../" and should be updated
https://repology.org/repository/nix_stable/problems

pkgs/development/libraries/git2/default.nix

@@ -27,7 +27,7 @@ stdenv.mkDerivation (rec {
 
   meta = {
     description = "The Git linkable library";
-    homepage = http://libgit2.github.com/;
+    homepage = https://libgit2.github.com/;
     license = stdenv.lib.licenses.gpl2;
     platforms = with stdenv.lib.platforms; all;
   };