lefthook: use go 1.14 to build

Due to some changes in `go` from 1.14 to 1.15 the lefthook tool
currently can't start external programs and errors each test it tries
to run, making it effectively useless.

This is a temporary fix to make `lefthook` usable again until the
upstream issue was fixed and a new release has been cut.

Upstream issue: https://github.com/Arkweid/lefthook/issues/151

pkgs/applications/version-management/git-and-tools/lefthook/default.nix

@@ -1,5 +1,11 @@
 { stdenv, buildGoModule, fetchFromGitHub }:
 
+# Currently `buildGo114Module` is passed as `buildGoModule` from
+# `../default.nix`. Please remove the fixed 1.14 once a new release has been
+# made and the issue linked below has been closed upstream.
+
+# https://github.com/Arkweid/lefthook/issues/151
+
 buildGoModule rec {
   pname = "lefthook";
   version = "0.7.2";