minor symfony#21309 [Serializer] Add missing conflict for property-info<3.1 (chalasr)

This PR was merged into the 3.1 branch.

Discussion
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[Serializer] Add missing conflict for property-info<3.1

| Q             | A
| ------------- | ---
| Branch?       | 3.1
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#21293 (comment)
| License       | MIT
| Doc PR        | n/a

Commits
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60a0c4b [Serializer] Add missing conflict for property-info<3.1

Author: nicolas-grekas

src/Symfony/Component/Serializer/composer.json

@@ -30,7 +30,8 @@
         "phpdocumentor/reflection-docblock": "~3.0"
     },
     "conflict": {
-        "symfony/property-access": ">=3.0,<3.0.4|>=2.8,<2.8.4"
+        "symfony/property-access": ">=3.0,<3.0.4|>=2.8,<2.8.4",
+        "symfony/property-info": "<3.1"
     },
     "suggest": {
         "psr/cache-implementation": "For using the metadata cache.",