Removed litmus-portal and moved upgrade agents

[Saranya-jena]

Removing Litmus-portal directory as it has been deprecated and not being since the release of Litmus 3.0.0. The Litmus-portal has been revamped as Chaoscenter with the release of the 3.0.0 and can be found out here. Users can still be able to use 2.x.x with images available in docker.

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[prithvi1307]

lgtm