Fix bad `gen` in npm bridges script
Fix bad `gen` in npm bridges script

The gen directory doesn't exist any more, we generate to the same dir as
the source code.

Change-Id: Icf90df81c3c8cdbd849de116633c14a28b164046
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2479135
Commit-Queue: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@chromium.org>
Commit-Queue: Tim van der Lippe <dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org>
Auto-Submit: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@chromium.org>
Reviewed-by: Tim van der Lippe <dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org>

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