Stabilize the flaky iframe test

The test above this one loads hello.txt, but we don't wait for the "load
finished" message, so it can arrive after the previous test already finished and
make this test not wait properly.

However, we also can't easily wait for the load finished message in the
previous test as it only appears with QtWebEngine, not QtWebKit.

As a workaround, we simply load another file in that test, to circumvent this
kind of cross-interaction.

tests/end2end/data/hints/iframe_target.html

@@ -9,6 +9,7 @@
         <iframe id="my-iframe"></iframe>
         <p>
             A <a href="/data/hello.txt" target="my-iframe">link</a> to be opened in the iframe above.
+            A <a href="/data/hello2.txt" target="my-iframe">second link</a> for the iframe.
         </p>
     </body>
 </html>

tests/end2end/features/hints.feature

@@ -239,12 +239,11 @@ Feature: Using hints
     Scenario: Opening a link with specific target frame in a new tab
         When I open data/hints/iframe_target.html
         And I run :tab-only
-        And I hint with args "links tab" and follow a
-        And I wait until data/hello.txt is loaded
-        And I wait 0.5s
+        And I hint with args "links tab" and follow s
+        And I wait until data/hello2.txt is loaded
         Then the following tabs should be open:
             - data/hints/iframe_target.html
-            - data/hello.txt (active)
+            - data/hello2.txt (active)
 
     Scenario: Clicking on iframe with :hint all current
         When I open data/hints/iframe.html