Clarify Token Handling section description (modelcontextprotocol#558)

Signed-off-by: Takashi Norimatsu <[email protected]>

Author: tnorimat

docs/specification/draft/basic/authorization.mdx

@@ -479,7 +479,7 @@ response.
 
 MCP clients **MUST NOT** send tokens to the MCP server other than ones issued by the MCP server's authorization server.
 
-Authorization servers **MUST** only accept tokens that are valid for use with their
+MCP servers **MUST** only accept tokens that are valid for use with their
 own resources.
 
 MCP servers **MUST NOT** accept or transit any other tokens.