Default parse_mode not working for send_animation method
## Context
* Operating System: Linux, MacOS
* Python Version: 3.7.7
* aiogram version: 2.6.1
* aiohttp version: 3.6.2
* uvloop version (if installed): 0.14.0

## Expected Behavior
1. Set default parse mode for bot: Bot(..., parse_mode=ParseMode.HTML)
2. Call send_animation method without parse_mode param.
3. Caption parsed with default parse_mode from step 1.

## Current Behavior
1. Set default parse mode for bot: Bot(..., parse_mode=ParseMode.HTML)
2. Call send_animation method without parse_mode param.
3. Caption NOT parsed

diff --git a/aiogram/bot/bot.py b/aiogram/bot/bot.py
index 39313558..c7b6dcbe 100644
--- a/aiogram/bot/bot.py
+++ b/aiogram/bot/bot.py
@@ -523,6 +523,8 @@ class Bot(BaseBot, DataMixin, ContextInstanceMixin):
         """
         reply_markup = prepare_arg(reply_markup)
         payload = generate_payload(**locals(), exclude=["animation", "thumb"])
+        if self.parse_mode:
+            payload.setdefault('parse_mode', self.parse_mode)
 
         files = {}
         prepare_file(payload, files, 'animation', animation)
['aiogram/bot/bot.py']