Bump version to 2.61.0-dev #4741

Job	Run time
Prepare CodeQL unit test matrix	4s
Run unit tests (cpp, 2.21.4, codeql-cli/v2.21.4, codeql-bundle-v2.21.4, ubuntu-latest-xl, codeql-...	2h 23m 30s
Run unit tests (c, 2.21.4, codeql-cli/v2.21.4, codeql-bundle-v2.21.4, ubuntu-latest-xl, codeql-cl...	45m 38s
Validate test results	6s
	3h 9m 18s

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