Remove php 5.6 from the latest wp test matrix

.github/workflows/test.yml

@@ -25,7 +25,7 @@ jobs:
       matrix:
         # Notes regarding supported versions in WP:
         # The base matrix only contains the PHP versions which are supported on all supported WP versions.
-        php: ['5.6', '7.0', '7.1', '7.2', '7.3']
+        php: ['7.0', '7.1', '7.2', '7.3']
         wp: ['latest', '5.2']
         experimental: [false]
 
@@ -50,6 +50,9 @@ jobs:
           - php: '7.3'
             wp: '5.3'
             experimental: false
+          - php: '5.6'
+            wp: '5.2'
+            experimental: false
           - php: '5.6'
             wp: '5.5'
             experimental: false