Stop testing on 7.2

We are seeing random failures from the GitHub Action setup unrelated
to our code. 7.2 was EOL'd quite some time ago. I am not dropping
support completely as this library gets packaged and distributed
for various distribution that are still on old PHP versions.

Author: oschwald

.github/workflows/test.yml

@@ -14,7 +14,7 @@ jobs:
       matrix:
         arch: ["amd64", "i386"]
         operating-system: [ubuntu-latest]
-        php-versions: ['7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
+        php-versions: ['7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
         php-extensions: ['bcmath', 'gmp']
     name: "PHP ${{ matrix.php-versions }} (with ${{ matrix.php-extensions }}) test on ${{ matrix.operating-system }}/${{ matrix.arch }}"
     steps: