minor #6033 Fix Typo (Shine-neko)

This PR was submitted for the 3.0 branch but it was merged into the 2.3 branch instead (closes #6033).

Discussion
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Fix Typo

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no

Commits
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1e1a49c Fix Typo

components/dependency_injection/synthetic_services.rst

@@ -32,7 +32,7 @@ service will get a "service does not exist" error).
 In order to do so, you have to use
 :method:`Definition::setSynthetic() <Symfony\\Component\\DependencyInjection\\Definition::setSynthetic>`::
 
-    use Symfony\Component\DependencyInjectino\Definition;
+    use Symfony\Component\DependencyInjection\Definition;
 
     // synthetic services don't specify a class
     $kernelDefinition = new Definition();