Auto merge of #12627 - metajack:win7-manifest, r=jdm

Fix missing namespace in Windows manifest

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- [ ] These changes fix #__ (github issue number if applicable).

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The <compatibility> tag must be in the right namespace, or Windows 7
throws an error.

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components/servo/servo.exe.manifest

@@ -6,7 +6,7 @@
                     name="servo.Servo"
                     version="0.1.0.0"/>
 
-  <compatibility>
+  <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
     <application>
       <supportedOS Id="{35138b9a-5d96-4fbd-8e2d-a2440225f93a}"/> <!-- Windows 7 -->
       <supportedOS Id="{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38}"/> <!-- Windows 8 -->