Remove temp leiningen testing workflow #429

Job	Run time
test-boot (ubuntu-latest)	12s
test-tools-deps (ubuntu-latest)	15s
test-clojure-cli (ubuntu-latest)	13s
test-clj-kondo (ubuntu-latest)	11s
test-cljstyle (ubuntu-latest)	11s
test-bb (ubuntu-latest)	12s
test-zprint (ubuntu-latest)	9s
test-cljfmt (ubuntu-latest)	11s
test-clojure-cli-latest (ubuntu-latest)	13s
all-together	12s
test-leiningen (ubuntu-latest)	10s
	2m 9s

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