Fix Typos in Platform Support Tables

[qb42]

3 recently demoted targets had their entries moved to the tier 3 table without adjusting for the extra "host" column, this PR adds an empty column so they display correctly.

2 recently promoted targets had the opposite problem, also fixed.

While doing that I noticed that empty columns were represented inconsistently throughout the file so I normalized them all to be 2 spaces, which seemed to be the majority opinion (139 instances vs 5 for 1 space and 19 for 3 spaces).

Closes: #150499

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[Kobzol]

It would be great to write some test that parses this Markdown and ensures that the table format is correct. Maybe it could live in src/tools/tidy? (doesn't need to be in this PR)

[ChrisDenton]

Tbh I'd rather we go in the opposite direction and have the tables be automatically generated from metadata. But perhaps testing the markdown is a better short term solution.

[workingjubilee]

Thanks. As my colleagues note there's a larger improvement to be had here but right now, this change seems fine. No reason to pressgang someone sending a typo fix into making a larger PR.

@bors r+ rollup

[bors]

📌 Commit 841091b has been approved by workingjubilee

It is now in the queue for this repository.