minor symfony#22529 [Asset] Fix invalid assets.xml (nicolas-grekas)

This PR was merged into the 2.8 branch.

Discussion
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[Asset] Fix invalid assets.xml

| Q             | A
| ------------- | ---
| Branch?       | 2.8
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Fixes invalid xml definitions.

Commits
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de1b20a [Asset] Fix invalid assets.xml

Author: fabpot

src/Symfony/Bundle/FrameworkBundle/Resources/config/assets.xml

@@ -21,13 +21,13 @@
 
         <service id="assets.path_package" class="Symfony\Component\Asset\PathPackage" abstract="true">
             <argument /> <!-- base path -->
-            <argument type="service" /> <!-- version strategy -->
+            <argument /> <!-- version strategy -->
             <argument type="service" id="assets.context" />
         </service>
 
         <service id="assets.url_package" class="Symfony\Component\Asset\UrlPackage" abstract="true">
             <argument /> <!-- base URLs -->
-            <argument type="service" /> <!-- version strategy -->
+            <argument /> <!-- version strategy -->
             <argument type="service" id="assets.context" />
         </service>