Rephrased connection pool detection algorithm

Closes gh-5864

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -2478,8 +2478,9 @@ Here's the algorithm for choosing a specific implementation:
 
 * We prefer the Tomcat pooling `DataSource` for its performance and concurrency, so if
   that is available we always choose it.
-* If HikariCP is available we will use it.
-* If Commons DBCP is available we will use it, but we don't recommend it in production.
+* Otherwise, if HikariCP is available we will use it.
+* If neither the Tomcat pooling datasource nor HikariCP are available and if Commons DBCP
+  is available we will use it, but we don't recommend it in production.
 * Lastly, if Commons DBCP2 is available we will use it.
 
 If you use the `spring-boot-starter-jdbc` or `spring-boot-starter-data-jpa`