ci: Add Spring Boot 4.1.0-M4 milestone to CI matrix

[adinauer]

📜 Description

Add Spring Boot 4.1.0-M4 (latest milestone) to the 4.x CI matrix to catch compatibility issues early before GA.

💡 Motivation and Context

Spring Boot 4.1 is in milestone phase. Testing against it now surfaces breaking changes early so we can prepare ahead of the GA release.

💚 How did you test it?

CI will validate.

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

#skip-changelog

[github-actions]

Semver Impact of This PR

🟢 Patch (bug fixes)

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[sentry]

Sentry Build Distribution

App Name	App ID	Version	Configuration	Install Page
SDK Size	io.sentry.tests.size	8.37.0 (1)	release	Install Build

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	304.88 ms	342.82 ms	37.94 ms
Size	0 B	0 B	0 B

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
abfcc92	309.54 ms	380.32 ms	70.78 ms
b3d8889	371.84 ms	447.49 ms	75.65 ms
55aaf9b	341.96 ms	399.96 ms	58.00 ms
9139b91	351.35 ms	355.63 ms	4.28 ms
ee747ae	554.98 ms	611.50 ms	56.52 ms
674d437	355.28 ms	504.18 ms	148.90 ms
f064536	329.00 ms	395.62 ms	66.62 ms
ee747ae	415.92 ms	470.15 ms	54.23 ms
1df7eb6	397.04 ms	429.64 ms	32.60 ms
d217708	355.34 ms	381.39 ms	26.05 ms

App size

Revision	Plain	With Sentry	Diff
abfcc92	1.58 MiB	2.13 MiB	557.31 KiB
b3d8889	1.58 MiB	2.10 MiB	535.07 KiB
55aaf9b	0 B	0 B	0 B
9139b91	1.58 MiB	2.13 MiB	559.52 KiB
ee747ae	1.58 MiB	2.10 MiB	530.95 KiB
674d437	1.58 MiB	2.10 MiB	530.94 KiB
f064536	1.58 MiB	2.20 MiB	633.90 KiB
ee747ae	1.58 MiB	2.10 MiB	530.95 KiB
1df7eb6	1.58 MiB	2.10 MiB	532.97 KiB
d217708	1.58 MiB	2.10 MiB	532.97 KiB