ci: disable auto updates for `io_bazel_rules_webtesting` #599

Job	Run time
list	39s
workflow (devkit-core-tests)	29s
workflow (devkit-core-tests-rerun)	30s
workflow (build-cli)	32s
workflow (modules-builder-tests)	30s
workflow (build-unit-tests)	26s
	3m 6s

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