Update php to 7.3 in composer.json

composer.json

@@ -78,7 +78,7 @@
         }
     ],
     "require": {
-        "php": ">=7.0.8",
+        "php": ">=7.3",
         "browserstate/history.js": "1.8",
         "ckeditor/indentblock": "4.8.0",
         "cweagans/composer-patches": "^1.0",
@@ -305,7 +305,7 @@
         "preferred-install": "dist",
         "sort-packages": true,
         "platform": {
-            "php": "7.0.8"
+            "php": "7.3"
         }
     }
-}
+}
\ No newline at end of file