Revert "test: add ToProto and FromProto tests" (a2aproject#381)

Reverts a2aproject#341

Author: ehsavoie

spec-grpc/src/test/java/io/a2a/grpc/utils/FromProtoTest.java

@@ -289,28 +289,4 @@ public void convertTaskTimestampStatus() {
         assertNotNull(status.timestamp());
         assertEquals(expectedTimestamp, status.timestamp());
     }
-
-    @Test
-    public void testToProtoPartUnsupportedType() {
-        class FakePart extends io.a2a.spec.Part<Object> {
-            @Override
-            public io.a2a.spec.Part.Kind getKind() { return null; }
-            @Override
-            public Map<String, Object> getMetadata() { return Map.of(); }
-        }
-
-        FakePart fakePart = new FakePart();
-
-        io.a2a.spec.Message message = new io.a2a.spec.Message.Builder()
-                .messageId("msg-unsupported")
-                .contextId("ctx-unsupported")
-                .role(io.a2a.spec.Message.Role.USER)
-                .parts(List.of(fakePart))
-                .build();
-        io.a2a.grpc.Message result = ProtoUtils.ToProto.message(message);
-
-        assertNotNull(result);
-        assertEquals(1, result.getContentCount());
-    }
-
 }