fix: docker build issue

[lechnerc77]

Purpose

• Fix Docker build issue by pinning CF MTA Plugin. See cf deploy issue with new mta plugin 3.2.1 being released cloudfoundry/multiapps-cli-plugin#186 for details

Does the PR solve an issue

[ ] Yes - Please add issue number
[X] No

Does this introduce a breaking change?

[ ] Yes
[X] No

Pull Request Type

What kind of change does this Pull Request introduce?

[X] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

What to Check

Docker Build is executed successfully

Other Information

n/a