Do not cancel context on Connection.Close (elastic#40769)

This commit removes a call to conn.cancelReqs() that causes the
Connection to be unusable after Close() is called, leading to the bug
described by elastic#40705.

libbeat/esleg/eslegclient/connection.go

@@ -326,7 +326,6 @@ func (conn *Connection) Ping() (ESPingData, error) {
 // Close closes a connection.
 func (conn *Connection) Close() error {
 	conn.HTTP.CloseIdleConnections()
-	conn.cancelReqs()
 	return nil
 }