Add php unit composer dependencies to Makefile

[phil-davis]

Description

If I clone this repo and immediately make test-php-unit it dies. I first need to know to do composer install or some other make target that will install the composer dependencies.

Add the composer dependencies so that make test-php-unit will "just work"

(I noticed this when sorting out Makefile for the metrics app)

How Has This Been Tested?

Local make test-php-unit

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [x] tests only

Checklist:

• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

[codecov[bot]]

Codecov Report

Merging #154 into master will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #154   +/-   ##
=========================================
  Coverage     18.93%   18.93%           
  Complexity      268      268           
=========================================
  Files            24       24           
  Lines          1183     1183           
=========================================
  Hits            224      224           
  Misses          959      959

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