[infra] Update bazel image to Cockroach 20.2.8

A different CL will update the CIPD version.

Change-Id: I12f885fb20a3036b87096cc220daec10600e0377
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/404800
Reviewed-by: Leandro Lovisolo <lovisolo@google.com>
diff --git a/BUILD.bazel b/BUILD.bazel
index 11e8d38..d5f5dc5 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -192,8 +192,8 @@
 
         # Install CockroachDB as per the instructions here:
         # https://www.cockroachlabs.com/docs/v20.2/install-cockroachdb-linux.
-        "wget -qO- https://binaries.cockroachdb.com/cockroach-v20.2.4.linux-amd64.tgz | tar xvz",
-        "cp -i cockroach-v20.2.4.linux-amd64/cockroach /usr/local/bin/",
+        "wget -qO- https://binaries.cockroachdb.com/cockroach-v20.2.8.linux-amd64.tgz | tar xvz",
+        "cp -i cockroach-v20.2.8.linux-amd64/cockroach /usr/local/bin/",
 
         # Install depot_tools, necessary to pull binaries via CIPD.
         "git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git /depot_tools",