V8: Make win-clang a tree closer.

scripts/slave/gatekeeper.json

 {
   "comment": ["This is a configuration file for gatekeeper_ng.py",
               "Look at that for documentation on this file's format."],
 
   "masters": {
     "https://build.chromium.org/p/chromium": [
       {
         "categories": [
           "chromium_tree_closer"
         ],
@@ skipping 596 matching lines @@
           "v8_all"
         ],
         "excluded_builders" : [
           "V8 Linux - swarming staging",
           "V8 Linux - debug - greedy allocator",
           "V8 Linux64 - debug - greedy allocator",
           "V8 Linux64 - cfi",
           "V8 Linux64 - gcov coverage",
           "V8 Linux - full debug",
           "V8 Linux - interpreted regexp",
-          "V8 Random Deopt Fuzzer - debug",
-          "V8 Win64 - clang"
+          "V8 Random Deopt Fuzzer - debug"
         ],
         "builders": {
           "V8 Linux - predictable": {
             "excluded_steps": [
               "Mjsunit",
               "Webkit",
               "Benchmarks",
               "Test262",
               "Mozilla"
             ]
@@ skipping 333 matching lines @@
         "cleanup_temp",
         "taskkill"
       ],
       "closing_optional": [
         "compile",
         "gn"
       ]
     }
   }
 }