chore(deps-dev): bump heroku/heroku-buildpack-php in /tests/apps/php

Bumps [heroku/heroku-buildpack-php](https://github.com/heroku/heroku-buildpack-php) from 166 to 169.
- [Release notes](https://github.com/heroku/heroku-buildpack-php/releases)
- [Changelog](https://github.com/heroku/heroku-buildpack-php/blob/master/CHANGELOG.md)
- [Commits](https://github.com/heroku/heroku-buildpack-php/compare/v166...v169)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

tests/apps/php/composer.lock

@@ -996,16 +996,16 @@
     "packages-dev": [
         {
             "name": "heroku/heroku-buildpack-php",
-            "version": "v166",
+            "version": "v169",
             "source": {
                 "type": "git",
                 "url": "https://github.com/heroku/heroku-buildpack-php.git",
-                "reference": "8d807ac5975ec17c4d49b60982a7bebe1ae70dac"
+                "reference": "e87b635929a8b51c6f2d459cde1a241e478d3d04"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/heroku/heroku-buildpack-php/zipball/8d807ac5975ec17c4d49b60982a7bebe1ae70dac",
+                "url": "https://api.github.com/repos/heroku/heroku-buildpack-php/zipball/e87b635929a8b51c6f2d459cde1a241e478d3d04",
-                "reference": "8d807ac5975ec17c4d49b60982a7bebe1ae70dac",
+                "reference": "e87b635929a8b51c6f2d459cde1a241e478d3d04",
                 "shasum": ""
             },
             "bin": [
@@ -1036,7 +1036,7 @@
                 "nginx",
                 "php"
             ],
-            "time": "2019-12-20T10:56:23+00:00"
+            "time": "2020-01-26T11:19:01+00:00"
         }
     ],
     "aliases": [],