docs: correct create_mcp_http_client default timeout docstring

The docstring claimed the default timeout is 30 seconds, but the
implementation sets httpx.Timeout(30, read=300) so the read timeout is
actually 5 minutes to accommodate long-lived SSE streams. Update the
docstring to reflect the real defaults.

Author: aryanmotgi

src/mcp/shared/_httpx_utils.py

@@ -29,12 +29,14 @@ def create_mcp_http_client(
 
     This function provides common defaults used throughout the MCP codebase:
     - follow_redirects=True (always enabled)
-    - Default timeout of 30 seconds if not specified
+    - Default timeout of 30 seconds for connect/write/pool and 300 seconds for read (to
+      accommodate long-lived SSE streams) if not specified
 
     Args:
         headers: Optional headers to include with all requests.
         timeout: Request timeout as httpx.Timeout object.
-            Defaults to 30 seconds if not specified.
+            Defaults to 30 seconds for connect/write/pool and 300 seconds for read if
+            not specified.
         auth: Optional authentication handler.
 
     Returns: