fix(docs) Updated the name from v2 to OIP

[Rajakavitha1]

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:
I have not updated the references in https://github.com/SeldonIO/seldon-core/blob/f993cbb2c96043168ee59b1d6386ec3880f42eb3/notebooks/explainer_examples_v2.ipynb. This I hope the developer does.

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✅ Rajakavitha1
❌ Rakavitha Kodhandapani

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[matthewlowdon]

Fine, but I added one comment to consider.

[lc525]

Added suggestions to remove "incubating" in a number of places. The OIP is now established and the only thing we'd like to support moving forward.