[gold] Update probersk.json5 to hit /json/v2/expectations instead of v1.
[gold] Update probersk.json5 to hit /json/v2/expectations instead of v1.

Currently there's traffic still going to /json/v1/expectations, but it's not easy to determine where it's coming from:

https://thanos-query.skia.org/graph?g0.range_input=2d&g0.max_source_resolution=0s&g0.expr=gold_rpc_call_counter%7Broute%3D%22%2Fexpectations%22%2C%20version%3D%22v1%22%7D&g0.tab=0

By updating probersk.json5 to target /json/v2/expectations (which we need to do anyway), I hope to see the traffic to /json/v1/expectations drop to 0, in which case we'll know it's safe to delete said RPC.

Bug: skia:10522
Change-Id: I2e63d91ea63a16a03b71979d2abe6cae72ec3f85
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/333697
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