Fixes <https://issues.guix.gnu.org/56864>, which is a regression introduced
with a0beb297a352930b89051ff258a06d78f224d6b9.
* gnu/packages/web-browsers.scm (qutebrowser)
[phases]{wrap-qt-process-path}: Do not use the (no longer valid)
"qtwebengine-5" label; instead, locate QtWebEngineProcess via
'search-input-file'.
Reported-by: Jack Hill <jackhill@jackhill.us>