Bump sphinx-scylladb-theme from 1.8.4 to 1.8.5 in /docs #855

Job	Run time
Setup ITs	5s
Full verify (8)	1m 36s
Build (8)	1m 5s
Unit tests (8)	2m 4s
Scylla ITs (ENTERPRISE-RELEASE, 8)	10m 45s
Scylla ITs (ENTERPRISE-PRIOR-RELEASE, 8)	29m 27s
Cassandra ITs (RELEASE-3.X, 8)	19m 50s
Scylla ITs (OSS-RELEASE, 8)	10m 46s
Cassandra ITs (RELEASE-4.X, 8)	21m 10s
Scylla ITs (OSS-PRIOR-RELEASE, 8)	10m 29s
	1h 47m 17s

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