Update cargo_metadata requirement from 0.18 to 0.19 #2283

Job	Run time
maybe-expedite	5s
lint	4m 26s
test (third-party, bincode, stable)	10m 46s
test (third-party, bincode, nightly)	8m 5s
test (third-party, postcard, stable)	6m 40s
test (third-party, postcard, nightly)	8m 4s
test (other, bincode, stable)	24m 37s
test (other, bincode, nightly)	32m 19s
test (other, postcard, stable)	26m 14s
test (other, postcard, nightly)	32m 58s
all-checks	1s
	2h 34m 15s

Provide feedback