Fix floorplan for example Sky130 VLSI flow

[ethanwu10]

Update example floorplan used by Sky130 tutorials for changed SRAM instances.

EDIT: The YAML in example-designs also needs to be updated since it overrides vlsi/example-sky130.yml file when the tutorial= argument is passed to make. I've also found more issues with the layout stemming from margins not being aligned properly to the tracks, so I'll try to get all of these fixes rolled into this PR

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• Bug fix
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• Software change (RISC-V software)
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