Fix typos in HealthContributors definition

See spring-projectsgh-18249

Author: AlexFalappa

spring-boot-project/spring-boot-docs/src/main/asciidoc/production-ready-features.adoc

@@ -653,7 +653,7 @@ Spring Boot includes a number of auto-configured `HealthContributors` and you ca
 A `HealthContributor` can either be a `HealthIndicator` or a `CompositeHealthContributor`.
 A `HealthIndicator` provides actual health information, including a `Status`.
 A `CompositeHealthContributor` provides a composite of other `HealthContributors`.
-Taken together, contributor for a tree structure to represent the overall system heath.
+Taken together, contributors form a tree structure to represent the overall system health.
 
 By default, the final system health is derived by a `StatusAggregator` which sorts the statuses from each `HealthIndicator` based on an ordered list of statuses.
 The first status in the sorted list is used as the overall health status.