Bump paramiko to support diffie-hellman-group14-sha256 key exchange algo

This bump paramiko to 2.5.0, the first released version to support
diffie-hellman-group14-sha256 key exchange algorithm. It is needed to
work with current OpenBMC since c347ece05a7fdbf50d76cb136b9ed45caed333f6
poky commit disabled diffie-hellman-group14-sha1 in dropbear (for
security reasons) and so no common kex algos were left.

Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Change-Id: I72f99ffcad6ef0f2cde8a7904080388465ed03b7
diff --git a/requirements.txt b/requirements.txt
index 308b286..ff28a59 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,7 @@
 robotframework
 requests
 robotframework-requests>=0.3.9,<0.8.0
-paramiko>=2.3.2
+paramiko>=2.5.0
 robotframework-sshlibrary
 robotframework-scplibrary
 redfish