Fixed typos in the Servlet and Reactive Observability documents

[ximinghui]

In the Manual Configuration section of the Servlet and Reactive Observability documents, the ObservationRegistry class is incorrectly written: Type 'io. micrometer. observation. ObservationRegistry' does not have type parameters.

[jzheaux]

Hi, @ximinghui! Thanks for the PR.

Will you please update your commit message to be a bit shorter? This helps when people are reviewing the commit history in their IDE. I've updated your other PR to demonstrate an example.

If you want, you can add an explanation on a separate line like this:

A Short Title

A description that line-breaks at about 72 characters so that it
is easier to read in IDEs.

[jzheaux]

Thanks, @ximinghui! This is now merged into main