Specified that Maven must run with Java 8 in docs (#8706)

clients/hadoopfs/README.md

@@ -6,3 +6,8 @@ It uses the lakeFS server for metadata operations only.
 ## Publishing
 
 Follow the [HadoopFS release checklist](https://github.com/treeverse/dev/blob/main/pages/lakefs-clients-release.md#lakefs-hadoop-filesystem)
+
+## Building and Testing
+
+The project uses Maven.  
+**Prerequisite:** Java 8 must be installed for building and testing.

docs/project/contributing.md

@@ -39,9 +39,10 @@ Our [Go release workflow](https://github.com/treeverse/lakeFS/blob/master/.githu
    1. [Docker](https://docs.docker.com/get-docker/)
    1. [Go](https://golang.org/doc/install)
    1. [Node.js & npm](https://www.npmjs.com/get-npm)
-   1. [Maven](https://maven.apache.org/) to build and test Spark client codes.
    1. Java 8
       * Apple M1 users can install this from [Azul Zulu Builds for Java JDK](https://www.azul.com/downloads/?package=jdk). Builds for Intel-based Macs are available from [java.com](https://www.java.com/en/download/help/mac_install.html).
+   1. [Maven](https://maven.apache.org/) 
+      *  Required for building and testing Spark client code, as well as the hadoopfs client.
    1. *Optional* - [PostgreSQL 11](https://www.postgresql.org/docs/11/tutorial-install.html) (useful for running and debugging locally)
    1. *Optional* - [Rust & Cargo](https://www.rust-lang.org/tools/install) (useful for building the Rust SDK)
    1. *Optional* - [Buf CLI](https://buf.build/docs/installation) (only needed if you like to update Protocol Buffer files)