kvnemesis: bump the timeout

Medium -> large.

Closes #155985
Closes #155852

Epic: none

Release note: None

Author: arulajmani

pkg/kv/kvnemesis/BUILD.bazel

@@ -62,7 +62,7 @@ go_library(
 
 go_test(
     name = "kvnemesis_test",
-    size = "medium",
+    size = "large",
     srcs = [
         "applier_test.go",
         "engine_test.go",