Remove the _HEADER_NAME_FORBIDDEN constant

Author: timof1308

src/google/adk/tools/mcp_tool/_internal.py

@@ -48,10 +48,6 @@
 
 logger = logging.getLogger("google_adk." + __name__)
 
-# RFC 7230 compliant header patterns
-# Control characters and special characters not allowed in header names
-_HEADER_NAME_FORBIDDEN = r'\x00-\x1F\x7F()<>@,;:\\"/[\]?={} \t'
-
 # Header whitespace characters (RFC 7230 §3.2.4)
 _HEADER_WHITESPACE = "\r\n"