Supported php84 (#2984)

* Remove 5.x from supported versions

According to ./UPGRADE-1.0.md#php-5-eol, 5.x is no longer supported.

* Add 8.4 to supported versions

Without it, the installer script could only find the main binary
/usr/bin/php because it didn't had a version number included in the path.
Inspired by 7e6ff34

datadog-setup.php

@@ -2408,7 +2408,7 @@ function get_ini_settings($sourcesDir, $appsecHelperPath, $appsecRulesPath)
  */
 function get_supported_php_versions()
 {
-    return ['5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3'];
+    return ['7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4'];
 }
 
 main();