Run clang update script under python3 in webrtc DEPS file

Bug: chromium:1261812,webrtc:13318
Change-Id: I4ad4170eacc6f4864069e6790cabdfba85131bd9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/236420
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35267}
diff --git a/DEPS b/DEPS
index d562cda..e430a0e 100644
--- a/DEPS
+++ b/DEPS
@@ -2475,7 +2475,7 @@
     # Note: On Win, this should run after win_toolchain, as it may use it.
     'name': 'clang',
     'pattern': '.',
-    'action': ['python', 'src/tools/clang/scripts/update.py'],
+    'action': ['python3', 'src/tools/clang/scripts/update.py'],
   },
   {
     # Update LASTCHANGE.