Text from telegram custom json not saved to the tracker store
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**Rasa version**: 1.3.3

**Rasa X version** (if used & relevant):

**Python version**:

**Operating system** (windows, osx, ...):

**Issue**: 
I send a markdown message in telegram with `utter_custom_json`:
```python
dispatcher.utter_custom_json({
    "text": "*hello world*",
    "parse_mode": 'Markdown',
})
```
But only `parse_mode` field is saved in tracker store:
```python
{"data":
    {
        "attachment": None,
        "buttons": None,
        "custom": {"parse_mode": "Markdown"},
        "elements": None,
        "image": None,
        "quick_replies": None
    }
}
```



**Error (including full traceback)**:
```

```

**Command or request that led to error**:
```

```

**Content of configuration file (config.yml)** (if relevant):
```yml

```

**Content of domain file (domain.yml)** (if relevant):
```yml

```

diff --git a/rasa/core/channels/telegram.py b/rasa/core/channels/telegram.py
index 035dcd7c6d2..cdacb4afea8 100644
--- a/rasa/core/channels/telegram.py
+++ b/rasa/core/channels/telegram.py
@@ -1,4 +1,5 @@
 import logging
+from copy import deepcopy
 from sanic import Blueprint, response
 from sanic.request import Request
 from telegram import (
@@ -94,6 +95,8 @@ class TelegramOutput(Bot, OutputChannel):
     async def send_custom_json(
         self, recipient_id: Text, json_message: Dict[Text, Any], **kwargs: Any
     ) -> None:
+        json_message = deepcopy(json_message)
+
         recipient_id = json_message.pop("chat_id", recipient_id)
 
         send_functions = {
['rasa/core/channels/telegram.py']