Add Comments for CompactionWindow Config Advice (#6331)

## Which problem is this PR solving?
- Resolves #3466

## Description of the changes
- Added advice for CompactionWindow config

## Checklist
- [x] I have read
https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
- [x] I have signed all commits
- [ ] I have added unit tests for the new functionality
- [ ] I have run lint and test steps successfully
  - for `jaeger`: `make lint test`
  - for `jaeger-ui`: `yarn lint` and `yarn test`

Signed-off-by: Alok Kumar Singh <[email protected]>

pkg/cassandra/config/config.go

@@ -68,6 +68,8 @@ type Schema struct {
 	ReplicationFactor int `mapstructure:"replication_factor" valid:"optional"`
 	// CompactionWindow is the size of the window for TimeWindowCompactionStrategy.
 	// All SSTables within that window are grouped together into one SSTable.
+	// Ideally, operators should select a compaction window size that produces approximately less than 50 windows.
+	// For example, if writing with a 90 day TTL, a 3 day window would be a reasonable choice.
 	CompactionWindow time.Duration `mapstructure:"compaction_window" valid:"optional"`
 }