Make it clear to which type the DataSource properties are bound

See gh-20727

spring-boot-project/spring-boot-docs/src/main/groovy/generateConfigurationPropertyTables.groovy

@@ -56,7 +56,7 @@ def generateConfigMetadataDocumentation() {
 						"spring.jdbc", "spring.jpa")
 				.addOverride("spring.datasource.dbcp2", "Commons DBCP2 specific settings")
 				.addOverride("spring.datasource.tomcat", "Tomcat datasource specific settings")
-				.addOverride("spring.datasource.hikari", "Hikari specific settings")
+				.addOverride("spring.datasource.hikari", "Hikari specific settings bound to an instance of `HikariDataSource`")
 				.addSection("transaction")
 				.withKeyPrefixes("spring.jta", "spring.transaction")
 				.addSection("integration")