### What is this PR for?
Currently, the `how_to_build.md` documentation specifies that **Java 1.8** is required to build Zeppelin from source.
However, the project's root `pom.xml` file defines the `java.version` property as **11**.
This discrepancy can confuse new contributors, leading them to set up an incorrect development environment and encounter build failures.
f541b46115/pom.xml (L100)
- In `docs/setup/basics/how_to_build.md`:
- Change the required JDK version from `1.8` to `11`.
- Update the sample installation command from `openjdk-8-jdk` to `openjdk-11-jdk`.
### What type of PR is it?
Documentation
### Todos
* [x] - Update how_to_build.md docs
### What is the Jira issue?
[[ZEPPELIN-6303]](https://issues.apache.org/jira/browse/ZEPPELIN-6303)
### How should this be tested?
This is a trivial documentation update, so if the current CI passes, there’s no need for additional unit tests.
### Screenshots (if appropriate)
### Questions:
* Does the license files need to update? - No
* Is there breaking changes for older versions? - No
* Does this needs documentation? - No
Closes#5052 from hyunw9/ZEPPELIN-6303.
Signed-off-by: Cheng Pan <chengpan@apache.org>