Update subresource URL for `iframe-inheritance-data.html` WPT.

`Referrer-Policy` test subresources moved out of //referrer-policy, into
//common so that they could be used by other tests more easily. When we
did so, we neglected to update the URL in
//external/wpt/referrer-policy/generic/inheritance/iframe-inheritance-data.html.
This patch addresses that oversight.

Change-Id: I1989df8dc4e39ad26de8ac9562f81796bda5aebe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2003311Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Commit-Queue: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732333}

third_party/blink/web_tests/external/wpt/referrer-policy/generic/inheritance/iframe-inheritance-data-expected.txt

-This is a testharness.js-based test.
-FAIL iframes with data url uses no referrer assert_equals: expected (undefined) undefined but got (string) "FAILURE"
-Harness: the test ran to completion.
-

third_party/blink/web_tests/external/wpt/referrer-policy/generic/inheritance/iframe-inheritance-data.html

@@ -24,7 +24,7 @@
             `data:text/html,<script src = "${BASE}/common/security-features/resources/common.sub.js"></` + `script>
             <script src = "${BASE}/referrer-policy/generic/referrer-policy-test-case.js"></` + `script>
             <script>
-              var urlPath = "/referrer-policy/generic/subresource/xhr.py";
+              var urlPath = "/common/security-features/subresource/xhr.py";
               var url = "${BASE}" + urlPath;
               requestViaXhr(url).then((msg) => {
                   parent.postMessage({referrer: msg.referrer}, "*")})