make message of exception in decoding oneof element clearer

Author: xiaozhikang0916

formats/protobuf/commonMain/src/kotlinx/serialization/protobuf/internal/ProtobufDecoding.kt

@@ -391,9 +391,7 @@ private class OneOfPolymorphicReader(
     override fun decodeTaggedString(tag: ProtoDesc): String = if (tag == POLYMORPHIC_NAME_TAG) {
         // todo return a serial name for polymorphic serializer
         descriptor.getActualOneOfSerializer(parentTag.protoId)?.serialName ?: throw SerializationException(
-            "Cannot find a subclass of ${descriptor.serialName} in property \"${
-                descriptor.serialName
-            }\" annotated with @ProtoNumber(${parentTag.protoId})."
+            "Cannot find a subclass of ${descriptor.serialName} annotated with @ProtoNumber(${parentTag.protoId})."
         )
     } else {
         super.decodeTaggedString(tag)

formats/protobuf/commonTest/src/kotlinx/serialization/protobuf/ProtobufOneOfTest.kt

@@ -367,9 +367,7 @@ class ProtobufOneOfTest {
 
     @Test
     fun testFailWithClassDecoding() {
-        assertFailsWith<SerializationException>(
-            "Cannot find a subclass of kotlinx.serialization.protobuf.ProtobufOneOfTest.IFailType in property \"i\" annotated with @ProtoNumber(1)."
-        ) {
+        assertFailsWith<SerializationException> {
             ProtoBuf.decodeFromHexString<FailWithClass>(
                 "082a1a03666f6f"
             )