minor #21779 [Form][Serializer] Add missing conflicts for DI (chalasr)

This PR was merged into the 3.3-dev branch.

Discussion
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[Form][Serializer] Add missing conflicts for DI

| Q             | A
| ------------- | ---
| Branch?       | master
| Tests pass?   | yes
| Fixed tickets | https://github.com/symfony/symfony/pull/21375#discussion_r103180920
| License       | MIT

They make use of `PriorityTaggedServiceTrait` which is available since 3.2 only

Commits
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ddae4eff50 [Form][Serializer] Add missing conflicts for DI

src/Symfony/Component/Form/composer.json

@@ -36,6 +36,7 @@
     },
     "conflict": {
         "phpunit/phpunit": "<4.8.35|<5.4.3,>=5.0",
+        "symfony/dependency-injection": "<3.2",
         "symfony/doctrine-bridge": "<2.7",
         "symfony/framework-bundle": "<2.7",
         "symfony/twig-bridge": "<2.7"

src/Symfony/Component/Serializer/composer.json

@@ -31,6 +31,7 @@
         "phpdocumentor/reflection-docblock": "~3.0"
     },
     "conflict": {
+        "symfony/dependency-injection": "<3.2",
         "symfony/property-access": ">=3.0,<3.0.4|>=2.8,<2.8.4",
         "symfony/property-info": "<3.1",
         "symfony/yaml": "<3.1"