[workflow] Update php version

Author: Quan Zhao

.github/workflows/ngx_php.yml

@@ -29,7 +29,7 @@ jobs:
  --health-retries=3
 strategy:
 matrix:
-php_version: [7.0.33, 7.1.33, 7.2.34, 7.3.26, 7.4.15, 8.0.2]
+php_version: [7.0.33, 7.1.33, 7.2.34, 7.3.28, 7.4.19, 8.0.6]
 ngxinx_version: [1.12.2, 1.16.1]
 steps:
  - uses: actions/checkout@v2