Use HikariCP is jdbc and jpa starters

This commit is a companion of what was done in #6013. As HikariCP is
now the default connection pool, the jdbc and jpa starters no longer
provide `tomcat-jdbc`, but rather `HikariCP`.

Closes gh-9392

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

@@ -2829,7 +2829,7 @@ Here's the algorithm for choosing a specific implementation:
   DBCP2 is available we will use it.
 
 If you use the `spring-boot-starter-jdbc` or `spring-boot-starter-data-jpa`
-'`starters`' you will automatically get a dependency to `tomcat-jdbc`.
+'`starters`' you will automatically get a dependency to `HikariCP`.
 
 NOTE: You can bypass that algorithm completely and specify the connection pool to use via
 the `spring.datasource.type` property. This is especially important if you are running