ci: upgrade to pnpm 9

[hanspagel]

Let’s use pnpm 9 in CI. :)

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: a36205a9f71923708804ecf2337b35e0c73e91f0

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[relativeci[bot]]

#99 Bundle Size — 114.47KiB (+0.01%).

a36205a(current) vs 21b6fc0 main#98(baseline)

Bundle metrics   2 changes 1 regression

	Current #99	Baseline #98
Initial JS	114.47KiB(+0.01%)	114.45KiB
Initial CSS	0B	0B
Cache Invalidation	1.66%	0%
Chunks	45	45
Assets	45	45
Modules	45	45
Duplicate Modules	0	0
Duplicate Code	0%	0%
Packages	0	0
Duplicate Packages	0	0

Bundle size by type   1 change 1 regression

|            |       Current
[#99](https://app.relative-ci.com/projects/hXQ54UQKluDUZAKvpt9b/jobs/99-srNZtL0vzhs2OCUWI40m?utm_source=github&utm_medium=pr-report "View bundle analysis report") |      Baseline
[#98](https://app.relative-ci.com/projects/hXQ54UQKluDUZAKvpt9b/jobs/98-AK38bFH6L3Gd2tbS4tVd?utm_source=github&utm_medium=pr-report "View baseline bundle analysis report") | |:--|--:|--:| |   [JS](https://app.relative-ci.com/projects/hXQ54UQKluDUZAKvpt9b/jobs/99-srNZtL0vzhs2OCUWI40m/assets?ba=%7B%22filters%22%3A%22ft.CSS-0_ft.JS-1_ft.IMG-0_ft.MEDIA-0_ft.FONT-0_ft.HTML-0_ft.OTHER-0%22%7D "View JS assets") | `114.47KiB` (`+0.01%`) | `114.45KiB` |

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Bundle analysis report Branch ci/pnpm-9 Project dashboard

[hanspagel]

Close in favor of #132.