Add missing ElastiCache node type: cache.r6gd.large (#971)

* Initial plan

* Add missing ElastiCache node types (r6gd.large and r7gd series) and update .gitignore

Co-authored-by: wata727 <[email protected]>

* Remove cache.r7gd entries - not supported for ElastiCache Redis

Co-authored-by: wata727 <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: wata727 <[email protected]>

Author: Copilot

rules/utils.go

@@ -64,6 +64,7 @@ var validElastiCacheNodeTypes = map[string]bool{
 	"cache.r6g.8xlarge":   true,
 	"cache.r6g.12xlarge":  true,
 	"cache.r6g.16xlarge":  true,
+	"cache.r6gd.large":    true,
 	"cache.r6gd.xlarge":   true,
 	"cache.r6gd.2xlarge":  true,
 	"cache.r6gd.4xlarge":  true,