Bug 1127920 - Re-enable mediasource-redundant-seek.html with longer timeout, r=me

testing/web-platform/meta/media-source/mediasource-redundant-seek.html.ini

@@ -1,13 +1,12 @@
 [mediasource-redundant-seek.html]
   type: testharness
-  disabled:
-    if (os == "win") and (version != "5.1.2600"): frequent timeouts
   expected:
     if (os == "win") and (version != "5.1.2600"): OK
     if os == "mac": OK
     TIMEOUT
   [Test redundant fully prebuffered seek]
     expected:
+      if (os == "win") and (version != "5.1.2600"): PASS
       if os == "mac": PASS
       TIMEOUT