toolchain_utils: replace gsutil with gsutil.py

Remove dependency on pre-installed gLinux software.
gsutil.py comes from depot_tools which is part of chrotomation setup.

BUG=None
TEST=tested locally on chrotomation.mtv

Change-Id: I8fcef35a3c229ec06639a56b02c5751b4cedfc95
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2460835
Reviewed-by: George Burgess <gbiv@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Tested-by: George Burgess <gbiv@chromium.org>
diff --git a/pgo_tools/monitor_pgo_profiles.py b/pgo_tools/monitor_pgo_profiles.py
index 8670167..cb41eb8 100755
--- a/pgo_tools/monitor_pgo_profiles.py
+++ b/pgo_tools/monitor_pgo_profiles.py
@@ -37,7 +37,7 @@
 def fetch_most_recent_profdata(arch: str) -> ProfdataInfo:
   result = subprocess.run(
       [
-          'gsutil',
+          'gsutil.py',
           'ls',
           '-l',
           f'gs://chromeos-toolchain-artifacts/llvm-pgo/{arch}/'