Pin Bazel to 5.1.0 (#10707)

diff --git a/kokoro/windows/bazel/build.bat b/kokoro/windows/bazel/build.bat
index 55fba16..9b4e448 100644
--- a/kokoro/windows/bazel/build.bat
+++ b/kokoro/windows/bazel/build.bat
@@ -10,7 +10,7 @@
 
 @rem Reinstall Bazel due to corrupt installation in kokoro.
 bazel version
-choco install bazel -y -i
+choco install bazel -y -i --version 5.1.0
 bazel version
 
 @rem Make paths as short as possible to avoid long path issues.