acc: set CloudSlow=true for lakebase/database-instance (#3507)

## Why
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might be missing.
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Reduces the number of tests that spin up a database instance that spin
up thus mitigating running into quota limits in workspaces

Author: anton-107

acceptance/bundle/deploy/lakebase/database-instance/single-instance/out.test.toml

@@ -1,5 +1,6 @@
 Local = true
 Cloud = true
+CloudSlow = true
 RequiresUnityCatalog = true
 
 [CloudEnvs]

acceptance/bundle/deploy/lakebase/database-instance/single-instance/test.toml

@@ -1,6 +1,9 @@
 Local = true
 Cloud = true
 
+# Mitigates running into quota limits in workspaces
+CloudSlow = true
+
 Ignore = [
     "databricks.yml",
 ]