Fix SiteIsolation.MainFrameWithTwoIFramesInTheSameProcess API test af…

…ter 265971@main

https://bugs.webkit.org/show_bug.cgi?id=259136
rdar://112118497

Unreviewed.

In my frenzy of copying and pasting, I inadvertently changed the test expectations.
This reverts that one line change.

* Tools/TestWebKitAPI/Tests/WebKitCocoa/SiteIsolation.mm:
(TestWebKitAPI::TEST):

Canonical link: https://commits.webkit.org/265983@main

Tools/TestWebKitAPI/Tests/WebKitCocoa/SiteIsolation.mm

@@ -935,7 +935,7 @@ HTTPServer server({
         EXPECT_NE(childFramePid, 0);
         EXPECT_NE(otherChildFramePid, 0);
         EXPECT_EQ(childFramePid, otherChildFramePid);
-        EXPECT_EQ(mainFramePid, childFramePid);
+        EXPECT_NE(mainFramePid, childFramePid);
         EXPECT_WK_STREQ(mainFrame.info.securityOrigin.host, "example.com");
         EXPECT_WK_STREQ(childFrame.info.securityOrigin.host, "webkit.org");
         EXPECT_WK_STREQ(otherChildFrame.info.securityOrigin.host, "webkit.org");