Bump gpb to 4.21.3

Author: tomas-abrahamsson

rebar.lock

@@ -1,8 +1,8 @@
 {"1.2.0",
-[{<<"gpb">>,{pkg,<<"gpb">>,<<"4.21.1">>},0}]}.
+[{<<"gpb">>,{pkg,<<"gpb">>,<<"4.21.3">>},0}]}.
 [
 {pkg_hash,[
- {<<"gpb">>, <<"72E229C242D252D690ADDCFD04A6416C26C4D4D2C3521E05570A7A78B48D3BD1">>}]},
+ {<<"gpb">>, <<"99CBD5BCE894E9287A8F351210AFDCD9D4B413087118A0D738B12A2D67D97591">>}]},
 {pkg_hash_ext,[
- {<<"gpb">>, <<"C05C9AEA9E25BD341367A43B3D3EB68E951563911072259C5EC4CB6642F4EF22">>}]}
+ {<<"gpb">>, <<"F31BF9EF24450C978E2010BCEC12272049E14F122511A7AE1488AEBA8A835158">>}]}
 ].