chore: Update MSRV to 1.91.0

[xanderbailey]

Which issue does this PR close?

#2199 requires a bump to MSRV 1.91.0. This version is within the policy of this project.

• Closes #.

What changes are included in this PR?

Are these changes tested?

[mbutrovich]

Thanks @xanderbailey!

[blackmwk]

Hi, @xanderbailey Following our discussion, our policy is to update msrv when relaseon a new version: https://github.com/apache/iceberg-rust?tab=readme-ov-file#supported-rust-version

[blackmwk]

We have a monthly release schedule plan, so we hope to release a new version soon

[xanderbailey]

Thanks, just so I understand correctly, is the plan always to bump MSRV after we release or before?

Because currently we're depending on a version of datafusion that has known bugs and correctness issues so releasing with 52.1 as a dependency would likely mean people would need to skip the 0.9.0 release.

[mbutrovich]

Thanks, just so I understand correctly, is the plan always to bump MSRV after we release or before?

Because currently we're depending on a version of datafusion that has known bugs and correctness issues so releasing with 52.1 as a dependency would likely mean people would need to skip the 0.9.0 release.

Last time we bumped MSRV just before the 0.8.0 release, so it was included in that. IIRC 0.8.0 and a DataFusion bump went in just before 0.8.0. I'm gonna start testing DF53 with iceberg-rust today as well (not released yet).

[blackmwk]

Thanks, just so I understand correctly, is the plan always to bump MSRV after we release or before?

Because currently we're depending on a version of datafusion that has known bugs and correctness issues so releasing with 52.1 as a dependency would likely mean people would need to skip the 0.9.0 release.

We usually bump it before the release. In this case I think it would be reasonable to bump it now, thanks for the explaination.

[blackmwk]

Thanks @xanderbailey for this fix!