ci: update rust version to 1.91.1 #353

Job	Run time
commit_lint / lint	12s
bundler_test / test	1m 18s
devcontainer / build	1m 56s
bundler_sqlx / prepare	3m 16s
docs_lint / lint	7s
helm_chart_lint / lint	15s
policy_test / test	5s
docs_build / build	23s
policy_lint / lint	8s
helm_chart_publish / publish (opa)	15s
helm_chart_publish / publish (bundler)	15s
policy_container	0s
techdocs_publish / publish	1m 3s
bundler_docs / build	1m 19s
bundler_lint / lint	1m 13s
bundler_lint / deny	21s
bundler_container / build_publish	5m 25s
pages_build / combine	5s
pages_publish / publish	22s
	17m 58s

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