Update minimal required version for the 'paramiko' package

Versions below 2.1.0 fail with the error
"Incompatible ssh peer (no acceptable kex algorithm)".

And versions below 2.3.2 fail with the Python versions above 3.7
because of the 'async' variable bug:
https://github.com/paramiko/paramiko/issues/1108

Therefore constrain minimal paramiko version to 2.3.2

Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>
Change-Id: Ia47dd0d82a916fc5e5fc440cd2b79607c892265a
diff --git a/requirements.txt b/requirements.txt
index 588a094..308b286 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,7 @@
 robotframework
 requests
 robotframework-requests>=0.3.9,<0.8.0
-paramiko==2.0.9
+paramiko>=2.3.2
 robotframework-sshlibrary
 robotframework-scplibrary
 redfish