[wptrunner] Declare linux-wpt-payments-fyi-rel as a trybot

This was an oversight in
https://chromium-review.googlesource.com/c/chromium/src/+/2425459

Bug: 1127055
Change-Id: If3fb89f024972f338cd81b16a1885af053aa594e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2429523Reviewed-by: Erik Staab <estaab@chromium.org>
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810404}

tools/mb/mb_config.pyl

@@ -927,6 +927,7 @@
       'linux-viz-rel': 'release_trybot',
       'linux-wpt-fyi-rel': 'release_trybot',
       'linux-wpt-identity-fyi-rel': 'release_trybot',
+      'linux-wpt-payments-fyi-rel': 'release_trybot',
       'linux-webkit-msan-rel': 'msan_release_bot',
       'linux_chromium_archive_rel_ng': 'release_bot',
       'linux_chromium_asan_rel_ng': 'asan_lsan_release_trybot',