Protocol Buffer update for release 2.3.x at Thu Apr 29 17:01:51 UTC 2021 (#3017)

* Update from https://github.com/corona-warn-app/cwa-protocol-buffers/commit/ade1bd9166337fecfe2da6c96e7f556ed834cd34

* Update from https://github.com/corona-warn-app/cwa-protocol-buffers/commit/20da593f00910a18bb92c97767a2d66033289091

* Update from https://github.com/corona-warn-app/cwa-protocol-buffers/commit/ab28912961716d8b7cb73d593397c2d8e3f0f466

Server-Protocol-Buffer/src/main/proto/internal/dgc/value_sets.proto

+// This file is auto-generated, DO NOT make any changes here
+syntax = "proto3";
+package de.rki.coronawarnapp.server.protocols.internal.dgc;
+
+
+message ValueSets {
+  // Vaccine or prophylaxis
+  ValueSet vp = 1;
+  // Vaccine medicinal product
+  ValueSet mp = 2;
+  // Marketing Authorization Holder
+  ValueSet ma = 3;
+}
+
+message ValueSet {
+  // use custom message instead of map to allow for future extensions
+  repeated ValueSetItem items = 1;
+}
+
+message ValueSetItem {
+  string key = 1;
+  string displayText = 2;
+}
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