Increase Windows shards

Rationale: The critical path in each of the current 8 windows shards is not as long as the overall Windows per-shard run time.
PiperOrigin-RevId: 883046605
Change-Id: I7d81c642ea0dd4be2e2d93ac46c49fdd78e89080

Author: ted-xie

.bazelci/presubmit.yml

@@ -184,7 +184,7 @@ tasks:
       - build
       - test
   windows:
-    shards: 8
+    shards: 10
     setup:
       - mkdir C:\b
       - mklink /J C:\b\bazeltest_external %OUTPUT_BASE:/=\%\external