build: update rules_browsers digest to 6a699bf #2145

Job	Run time
list	27s
workflow (devkit-core-tests-rerun)	1m 36s
workflow (build-cli)	1m 45s
workflow (modules-builder-tests)	1m 53s
workflow (build-unit-tests)	2m 33s
workflow (devkit-core-tests)	1m 26s
	9m 40s

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