ci: don't run codspeed in merge_group for now

[DaniPopes]

Not yet supported: CodSpeedHQ/runner#55

[codspeed-hq]

CodSpeed Performance Report

Merging #13483 will not alter performance

_{Comparing dani/no-codspeed-merge_group (4616138) with main (a9f835d)}

Summary

✅ 73 untouched benchmarks
🆕 4 new benchmarks
⁉️ 4 dropped benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	dani/no-codspeed-merge_group	Change
🆕	range lookup`	N/A	610 µs	N/A
🆕	any lookup`	N/A	19.9 ms	N/A
🆕	`prefix set	preload size: 1000	input size: 998	Vec with binary search lookup`
🆕	`prefix set	preload size: 1000	input size: 998	Vec with custom cursor lookup`
⁉️	range lookup`	609.1 µs	N/A	N/A
⁉️	any lookup`	19.4 ms	N/A	N/A
⁉️	`prefix set	preload size: 1000	input size: 999	Vec with binary search lookup`
⁉️	`prefix set	preload size: 1000	input size: 999	Vec with custom cursor lookup`

[mattsse]

feelsbadman