Update sdk.md with new ml_app naming guidelines

[barieom]

What does this PR do? What is the motivation?

Merge instructions

• [ ] Please merge after reviewing

Additional notes

[jhgilbert]

Hi @barieom, approved but I didn't merge it since the box isn't checked. When you want it merged, just ping me or the documentation channel. Also wanted to mention that your tests will always fail if your branch doesn't use a certain naming convention, described here. We have workarounds on the docs team, but those can slow down the acceptance of your PR. Thank you!