doc: updated Autovacuum Count metric description
@@ -1753,7 +1753,7 @@ Default config:
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- *Autovacuum Workers* calculates as summa of avtovacuum queries with not idle state.
+ *Autovacuum Workers* evaluates as count of `pg_stat_activity.backend_type = 'autovacuum worker'` for PG 10+ and as summa of avtovacuum queries with not idle state for PG 9.6 and lower.
## Background Writer
