ci: bump actions/checkout from 6 to 7 in the github-actions group #637

Job	Run time
Architecture and Documentation Guards	38s
Weekly Benchmark Diff	-1s
Test suite without poi-ooxml (optional-deps regression)	54s
Binary Compatibility (japicmp vs pom baseline)	43s
Performance Smoke Check	1m 21s
Build and run tests (JDK 17)	1m 16s
Build and run tests (JDK 21)	58s
Build and run tests (JDK 25)	57s
Examples Generation Smoke Test	1m 13s
	7m 59s

Provide feedback