[gold] skiacorrectness.go: Move frontendConfig next to frontendServerConfig.
[gold] skiacorrectness.go: Move frontendConfig next to frontendServerConfig.

This places the frontendConfig struct definition immediately after where it's first used.

Bug: skia:10816
Change-Id: I7a725de363898b3a31ab53f2d62293a431745f9a
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/323785
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>
Commit-Queue: Leandro Lovisolo <f558143c2568be8d55575d13f30a1fc5cb8009d5@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