fix: reserve main branch name

[majin1102]

Close #7167

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
rust/lance/src/dataset.rs	88.88%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[jackye1995]

I think this likely deserve a vote and also update the format spec accordingly?

[majin1102]

I think this likely deserve a vote and also update the format spec accordingly?

Yeah, sure.
I will update the format spec. This is actually an experience optimiziation. The real sematics has been established in earlier PRs. But I agree we coud have a vote to make this formal.

[github-actions]

Important

This PR touches the Lance format specification.

Substantive changes to the format specification — the .proto definitions
and the spec docs under docs/src/format/ — require a PMC vote before merge.
Minor edits such as typo fixes, wording, or formatting are excluded; use your
judgment.

If this is a meaningful format change:

• Start a vote following the Lance community voting process.
  Format specification modifications need 3 binding +1 votes (excluding the
  proposer), held on GitHub Discussions, with a minimum voting period of 1 week.
• Once the vote passes, link the completed vote in this PR. It should not be
  merged until the vote is linked.

[majin1102]

Related vote: #7229