Remove outdated key

The `spring.metrics.export.redis.aggregate-key-pattern` is no longer
defined but was still referenced in the documentation.

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -726,7 +726,6 @@ content into your application; rather pick only the properties that you need.
 	spring.metrics.export.send-latest=true # flag to switch off any available optimizations based on not exporting unchanged metric values
 	spring.metrics.export.includes= # list of patterns for metric names to include
 	spring.metrics.export.excludes= # list of patterns for metric names to exclude. Applied after the includes
-	spring.metrics.export.redis.aggregate-key-pattern= # pattern that tells the aggregator what to do with the keys from the source repository
 	spring.metrics.export.redis.prefix=spring.metrics # prefix for redis repository if active
 	spring.metrics.export.redis.key=keys.spring.metrics # key for redis repository export (if active)
 	spring.metrics.export.triggers.*= # specific trigger properties per MetricWriter bean name