Update python-dotenv requirement in /telegram_bot

Updates the requirements on [python-dotenv](https://github.com/theskumar/python-dotenv) to permit the latest version.
- [Release notes](https://github.com/theskumar/python-dotenv/releases)
- [Changelog](https://github.com/theskumar/python-dotenv/blob/main/CHANGELOG.md)
- [Commits](https://github.com/theskumar/python-dotenv/compare/v0.20.0...v0.21.0)

---
updated-dependencies:
- dependency-name: python-dotenv
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/dependabot.yml

@@ -10,8 +10,6 @@ updates:
     directory: "/api"
     schedule:
       interval: "daily"
-    assignees:
-      - "H4CK3R-01"
     open-pull-requests-limit: 100
 
   # Bot
@@ -19,10 +17,6 @@ updates:
     directory: "/telegram_bot"
     schedule:
       interval: "daily"
-    assignees:
-      - "NormalParameter"
-      - "Rripped"
-      - "FlorianKellermann"
     open-pull-requests-limit: 100
   
   # Frontend
@@ -30,6 +24,4 @@ updates:
     directory: "/frontend"
     schedule:
       interval: "daily"
-    assignees:
-      - "kevinpauer"
     open-pull-requests-limit: 100

telegram_bot/bot_updates.py

@@ -149,7 +149,6 @@ def update_for_user(p_user_id, p_my_handler):
     
     shares = p_my_handler.get_user_shares(p_user_id) # all interest shares
     
-    if shares!=None
     if len(share_symbols) != 0: # iterate through all shares
 
         for i in range(len(share_symbols)):

telegram_bot/requirements.txt

@@ -1,7 +1,7 @@
 pyTelegramBotAPI~=4.5.0
 Markdown~=3.3.6
 newsapi-python~=0.2.6
-python-dotenv~=0.20.0
+python-dotenv~=0.21.0
 requests~=2.27.1
 APScheduler~=3.9.1
 croniter~=1.3.4