Update for OR-3.4 - rebar3 -> 3.21

Author: martinsumner

rebar.config

@@ -51,7 +51,7 @@
         {deps, [
             {meck,
                 {git, "https://github.com/OpenRiak/meck.git",
-                    {branch, "openriak-3.2"}}},
+                    {branch, "openriak-3.4"}}},
             fqc
         ]},
         {erl_opts, [debug_info, {d, 'EQC'}]},
@@ -71,7 +71,7 @@
             {branch, "openriak-3.4"}}},
     {zstd, ".*",
         {git, "https://github.com/OpenRiak/zstd-erlang",
-            {branch, "openriak-3.2"}}},
+            {branch, "openriak-3.4"}}},
     {eqwalizer_support,
         {git_subdir, "https://github.com/OpenRiak/eqwalizer.git",
             {branch, "openriak-3.4"}, "eqwalizer_support"}}