highlight useful information on partitioned index page

Some of the information on the partition index page needs to be highlighted so it is easy to find.

e.g. a forum user asked how a partition key can be fixed if it gets mutated. 

https://forums.couchbase.com/t/cb-5-5-what-happens-when-index-partion-hashes-are-updated/16359/10

The answer is available on this page but is hard to find

https://docs.couchbase.com/server/6.0/n1ql/n1ql-language-reference/index-partitioning.html

The following needs to be highlighted:

If the partition keys have changed, then the corresponding document should be deleted and recreated with the new partition keys.