fix: remove UTF-8 BOM from url_validators.py

The BOM made ruff format flag the module on every pre-commit run. All
77 auth tests still pass.

Author: Varshith-Kali

src/mcp/server/auth/url_validators.py

@@ -1,4 +1,4 @@
-"""OAuth 2.0 URL validation helpers for MCP authorization servers.
+"""OAuth 2.0 URL validation helpers for MCP authorization servers.
 
 RFC 9700 4.1.1 and RFC 7591 2 require HTTPS for authorization endpoint URLs
 and registered redirect_uris, with an HTTP loopback exception for local