Bump gpb to 4.21.4

Author: tomas-abrahamsson

rebar.lock

@@ -1,8 +1,8 @@
 {"1.2.0",
-[{<<"gpb">>,{pkg,<<"gpb">>,<<"4.21.1">>},0}]}.
+[{<<"gpb">>,{pkg,<<"gpb">>,<<"4.21.4">>},0}]}.
 [
 {pkg_hash,[
- {<<"gpb">>, <<"72E229C242D252D690ADDCFD04A6416C26C4D4D2C3521E05570A7A78B48D3BD1">>}]},
+ {<<"gpb">>, <<"1BA426C2CE9D25AD6E2B279DE015644D22466FB874EADC0E442A1CF2DFA53EAB">>}]},
 {pkg_hash_ext,[
- {<<"gpb">>, <<"C05C9AEA9E25BD341367A43B3D3EB68E951563911072259C5EC4CB6642F4EF22">>}]}
+ {<<"gpb">>, <<"5F37AAA17CFCA4E09D81D95F79DF4CFED6FE25436000BC188E4E58881ED0298B">>}]}
 ].