update wording

Author: qingyang-hu

bson/decoder_test.go

@@ -647,7 +647,7 @@ func TestDecoderConfiguration(t *testing.T) {
 
 		var got objectIDTest
 		err := dec.Decode(&got)
-		const want = "error decoding key id: decoding an object ID into a plain string is not supported (set Decoder.ObjectIDAsHexString to enable decoding as a hexadecimal representation)"
+		const want = "error decoding key id: decoding an object ID into a string is not supported by default (set Decoder.ObjectIDAsHexString to enable decoding as a hexadecimal string)"
 		assert.EqualError(t, err, want)
 	})
 	t.Run("DefaultDocumentM top-level", func(t *testing.T) {

bson/string_codec.go

@@ -58,8 +58,8 @@ func (sc *stringCodec) decodeType(dc DecodeContext, vr ValueReader, t reflect.Ty
 			}
 			str = oid.Hex()
 		} else {
-			msg := "decoding an object ID into a plain string is not supported " +
-				"(set Decoder.ObjectIDAsHexString to enable decoding as a hexadecimal representation)"
+			const msg = "decoding an object ID into a string is not supported by default " +
+				"(set Decoder.ObjectIDAsHexString to enable decoding as a hexadecimal string)"
 			return emptyValue, errors.New(msg)
 		}
 	case TypeSymbol: