Bump shivammathur/setup-php from 2.27.1 to 2.28.0

Bumps [shivammathur/setup-php](https://github.com/shivammathur/setup-php) from 2.27.1 to 2.28.0.
- [Release notes](https://github.com/shivammathur/setup-php/releases)
- [Commits](shivammathur/setup-php@a36e1e5...e6f7513)

---
updated-dependencies:
- dependency-name: shivammathur/setup-php
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/exercise-lint-phpcs-psr-12.yml

@@ -27,7 +27,7 @@ jobs:
 
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11
 
-      - uses: shivammathur/setup-php@a36e1e52ff4a1c9e9c9be31551ee4712a6cb6bd0
+      - uses: shivammathur/setup-php@e6f75134d35752277f093989e72e140eaa222f35
         with:
           php-version: ${{ matrix.php-version }}
           extensions: gmp

.github/workflows/exercise-tests-phpunit-9.yml

@@ -27,7 +27,7 @@ jobs:
 
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11
 
-      - uses: shivammathur/setup-php@a36e1e52ff4a1c9e9c9be31551ee4712a6cb6bd0
+      - uses: shivammathur/setup-php@e6f75134d35752277f093989e72e140eaa222f35
         with:
           php-version: ${{ matrix.php-version }}
           extensions: gmp