Don't convert telegram chat_id

closes #5840

freqtrade/configuration/environment_vars.py

@@ -32,6 +32,7 @@ def flat_vars_to_nested_dict(env_dict: Dict[str, Any], prefix: str) -> Dict[str,
     :param prefix: Prefix to consider (usually FREQTRADE__)
     :return: Nested dict based on available and relevant variables.
     """
+    no_convert = ['CHAT_ID']
     relevant_vars: Dict[str, Any] = {}
 
     for env_var, val in sorted(env_dict.items()):
@@ -39,9 +40,9 @@ def flat_vars_to_nested_dict(env_dict: Dict[str, Any], prefix: str) -> Dict[str,
             logger.info(f"Loading variable '{env_var}'")
             key = env_var.replace(prefix, '')
             for k in reversed(key.split('__')):
-                val = {k.lower(): get_var_typed(val) if type(val) != dict else val}
+                val = {k.lower(): get_var_typed(val)
+                       if type(val) != dict and k not in no_convert else val}
             relevant_vars = deep_merge_dicts(val, relevant_vars)
-
     return relevant_vars