Fix typos and formatting errors in documentation

[ngocnhan-tran1996]

I fixed typo document

[philwebb]

Thanks. The tag::code[] comments should not be required, are you seeing problems with those samples?

[wilkinsona]

As shown in the docs, the Kotlin snippets are empty at the moment: https://docs.spring.io/spring-boot/reference/io/jta.html#io.jta.mixing-xa-and-non-xa-connections

[philwebb]

Thanks @wilkinsona. We might want to go the other way and update the Java samples to remove the code tag, that way imports can be shown in the sample.

[ngocnhan-tran1996]

@philwebb
I removed the code tag in Java sample and reverted Kotlin sample files in my machine. The result is the code snippets are empty, both Java and Kotlin

[wilkinsona]

I think the includes need to be updated as well to remove [tag=*].

[ngocnhan-tran1996]

Thanks @wilkinsona

It works. I will update PR

[philwebb]

Thanks very much @ngocnhan-tran1996