Ensure the sockets extension is on the list of extensions on CI

It should be included by default in PHP, though.

.github/workflows/run-tests.yml

@@ -24,7 +24,7 @@ jobs:
               uses: shivammathur/setup-php@v2
               with:
                   php-version: ${{ matrix.php }}
-                  extensions: posix, dom, curl, libxml, fileinfo, mbstring, zip, pcntl, pdo, sqlite, pdo_sqlite, bcmath, soap, intl, gd, exif, iconv, imagick
+                  extensions: posix, dom, curl, libxml, fileinfo, mbstring, zip, pcntl, pdo, sqlite, pdo_sqlite, bcmath, soap, intl, gd, exif, iconv, imagick, sockets
                   coverage: none
 
             - name: Install dependencies