Apply suggestions from code review

Co-authored-by: Kit Ewbank <[email protected]>

Author: tabito-hara

.changelog/44485.txt

@@ -1,3 +1,3 @@
 ```release-note:bug
-data-source/aws_lb: Fix panic caused by missing `secondary_ips_auto_assigned_per_subnet` attribute in schema definition
+data-source/aws_lb: Fix `Invalid address to set: []string{"secondary_ips_auto_assigned_per_subnet"}` errors
 ```