proto: remove support for unsigned field type

Part of tarantool/aeon#472

Author: ImeevMA

aeon_schema.proto

@@ -41,7 +41,6 @@ enum Engine {
 enum FieldType {
   FIELD_TYPE_UNSPECIFIED = 0;
   FIELD_TYPE_ANY = 1;
-  FIELD_TYPE_UNSIGNED = 2;
   FIELD_TYPE_STRING = 3;
   FIELD_TYPE_DOUBLE = 5;
   FIELD_TYPE_INTEGER = 6;

aeon_value.proto

@@ -40,7 +40,6 @@ message IntervalValue {
 // stored in the database.
 message Value {
   oneof kind {
-    uint64 unsigned_value = 1;
     string string_value = 2;
     double double_value = 3;
     sint64 integer_value = 4;