WebViewFindText::test_findTextManyMatches test failures

Test fails quite often according to grafana:

https://testresults.qt.io/grafana/d/000000009/coin-single-test-details?orgId=1&from=now-6M&to=now&var-project=qt%2Fqtwebengine&var-testcase=tests%2Fauto%2Fquick%2Fqmltests&var-testfunction=WebViewFindText::test_findTextManyMatches&var-branch=5.12&var-branch=5.13&var-branch=dev&var-inter=24h

The problems is with how QTBUG-61506 was solved here:

https://codereview.qt-project.org/c/qt/qtwebengine/+/198525

callback for findText called for id with previous test and that fails test