Move expiration of *.URLLoader.RequestInitiatorOriginLockCompatibility

We should keep the
NetworkService.URLLoader.RequestInitiatorOriginLockCompatibility
histogram until we are ready to start terminating renderers which submit
a request_initiator that is incompatible with
request_initiator_site_lock.

Bug: 967471
Change-Id: I7a6df884257aaeea15bf39cced24e8393e27e07a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1632556Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664619}

tools/metrics/histograms/histograms.xml

@@ -77482,7 +77482,7 @@ uploading your change for review.
 
 <histogram
     name="NetworkService.URLLoader.RequestInitiatorOriginLockCompatibility"
-    enum="RequestInitiatorOriginLockCompatibility" expires_after="2019-06-30">
+    enum="RequestInitiatorOriginLockCompatibility" expires_after="2020-06-30">
   <owner>creis@chromium.org</owner>
   <owner>jam@chromium.org</owner>
   <owner>lukasza@chromium.org</owner>