Remove duplication.
diff --git a/Doc/library/httplib.rst b/Doc/library/httplib.rst
index fc26f24..58b1bb7 100644
--- a/Doc/library/httplib.rst
+++ b/Doc/library/httplib.rst
@@ -452,7 +452,7 @@
    Set the host and the port for HTTP Connect Tunnelling. Normally used when
    it is required to do HTTPS Conection through a proxy server.
 
-   The headers argument should be a mapping of extra HTTP headers to to sent
+   The headers argument should be a mapping of extra HTTP headers to sent
    with the CONNECT request.
 
    .. versionadded:: 2.7