Remove second serve dependencies check

The second one isnt needed so long as the YAML import is 2nd. Once it tries to import serve it will fail and it's ImportError will get handled.

pywidevine/main.py

@@ -1,5 +1,4 @@
 import logging
-import sys
 from datetime import datetime
 from pathlib import Path
 from typing import Optional
@@ -299,16 +298,8 @@ def serve_(config: Path, host: str, port: int):
     Host as 127.0.0.1 may block remote access even if port-forwarded.
     Instead, use 0.0.0.0 and ensure the TCP port you choose is forwarded.
     """
-    try:
-        import yaml
     from pywidevine import serve
-    except ImportError:
-        print(
-            "Missing the extra dependencies for serve functionality. "
-            "You may install them under poetry with `poetry install -E serve`, "
-            "or under pip with `pip install pywidevine[serve]`."
-        )
-        sys.exit(1)
+    import yaml
 
     config = yaml.safe_load(config.read_text(encoding="utf8"))
     serve.run(config, host, port)