Update the version of protoc-gen-validate (#477)

This brings in https://github.com/lyft/protoc-gen-validate/pull/57 which
should allow builds that depend on data-plane-api (e.g. envoy) to work when git is
configured with a proxy.

Signed-off-by: Snow Pettersen <snowp@squareup.com>

bazel/repositories.bzl

@@ -3,7 +3,7 @@ GOGOPROTO_SHA = "342cbe0a04158f6dcb03ca0079991a51a4248c02" # Oct 7, 2017
 PROMETHEUS_SHA = "6f3806018612930941127f2a7c6c453ba2c527d2" # Nov 02, 2017
 OPENCENSUS_SHA = "993c711ba22a5f08c1d4de58a3c07466995ed962" # Dec 13, 2017
 
-PGV_GIT_SHA = "bd6d057e957fe184dfe76805951803af153be497"
+PGV_GIT_SHA = "d08da4114b44ba22f904906f8608c7593925ff0f"
 
 def api_dependencies():
     native.git_repository(