Update simple-game-server to 0.3

[roberthbailey]

Now that #2037 merged we need to push a new image of the simple game server (it will be the first multi-arch image).

/cc @jeremyje
/assign @roberthbailey

[markmandel]

Included with this, do we want to update:
https://github.com/googleforgames/agones/blob/main/examples/simple-game-server/Makefile#L109

Which is what prints out the image tag for release notes as well?

[roberthbailey]

If I update line 38 of that file I (to build and push the new image) I think that will do it, right?

[markmandel]

To probably phrase things in a more coherent manner - in the release notes, do we need to do anything special to say "these images are both linux and windows containers" ?

[roberthbailey]

@jeremyje and I had a chat about that this morning, and I think the conclusion is that we can mention it in the release notes but we shouldn't need to point to the linux & windows versions of the containers, just the multi-arch container.

@jeremyje said that "debian, alpine, ubuntu all use multi arch now" (in addition to a bunch of other common containers like golang) so we don't think this will be concerning for any of our users.

[roberthbailey]

This was done in #2048 and #2049.