minor #31655 Bump Symfony 5.0 to PHP 7.2 (nicolas-grekas)

This PR was merged into the 5.0-dev branch.

Discussion
----------

Bump Symfony 5.0 to PHP 7.2

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Not ready yet.

7.2 because it has all we need for the next two years (7.3 doesn't provide anything we absolutely need, and 7.4 is not even released so cannot be considered yet.)

7.2.9 because of https://tracker.debian.org/pkg/php7.2

Needs:
- [x] symfony/security-acl#48
- [x] doctrine/orm#7723
- [x] doctrine/DoctrineBundle#975
- [x] doctrine/DoctrineCacheBundle#158
- [x] symfony/symfony#31657

Commits
-------

72bd47e Bump Symfony 5.0 to PHP 7.2

Author: nicolas-grekas

composer.json

@@ -16,7 +16,7 @@
         }
     ],
     "require": {
-        "php": "^7.1.3"
+        "php": "^7.2.9"
     },
     "autoload": {
         "psr-4": { "Symfony\\Component\\Finder\\": "" },