minor symfony#20842 Fix upgrade notes (enumag)

This PR was submitted for the master branch but it was merged into the 3.2 branch instead (closes symfony#20842).

Discussion
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Fix upgrade notes

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

Commits
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d3b0044 Fix upgrade notes

Author: xabbuh

UPGRADE-3.2.md

@@ -70,7 +70,6 @@ FrameworkBundle
    in TwigBundle).
  * The service `serializer.mapping.cache.doctrine.apc` is deprecated. APCu should now
    be automatically used when available.
-   ```
 
 HttpFoundation
 ---------------
@@ -111,6 +110,7 @@ HttpKernel
    After:
    ```
    Surrogate-Capability: symfony="ESI/1.0"
+   ```
 
 Serializer
 ----------