deps: update dependency com.google.cloud:google-cloud-spanneradapter to v0.8.0 - abandoned #805

Job	Run time
javadoc	38s
units (21)	35s
units (8)	42s
units (11)	39s
units (17)	38s
windows	1m 18s
clirr	28s
dependencies (17)	35s
lint	30s
integration / integration-spanner (11)	8m 16s
integration / integration-cassandra (11)	3m 2s
	17m 21s

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