Fix prom2.skia.org nginx config.
Fix prom2.skia.org nginx config.

Bug: skia:
Change-Id: I2f199ec307e3aaa2817a51888f42cb31ee48639f
Reviewed-on: https://skia-review.googlesource.com/124703
Reviewed-by: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot