Java8 template: added openfaas dependencies

[PaulienVa]

Openfaas dependencies needed to make the Java8 template compile

Description

The command faas-cli new --lang java8 java-function generated a java project which was not compiling due to missing dependencies in the gradle file.

Motivation and Context

Change is required to assure that users (still) using Java8 can generate a proper function template. Although Java8 is end-of-life, it is still used.

Which issue(s) this PR fixes

-

How Has This Been Tested?

• Verified whether the Gradle build succeeds
• Build and deployed the function generated by the template on a local kubernetes cluster with OpenFaas installed. Function properly returned "Hello, world!"
• verify.sh succeeded

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)

Impact to existing users

Users using java8 can finally compile the generated template again

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I've read the CONTRIBUTION guide
• [x] I have signed-off my commits with git commit -s
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[derek[bot]]

Thank you for your contribution. I've just checked and your commit doesn't appear to be signed-off. That's something we need before your Pull Request can be merged. Please see our contributing guide. Tip: if you only have one commit so far then run: git commit --amend --signoff and then git push --force.