Roll depot_tools bleeding edge python versions.

This contains
https://chromium-review.googlesource.com/c/infra/infra/+/2943752 , a
stability fix for Mac (and potential startup performance improvement).

Bug: 1215121
Change-Id: Ifac20c066d7c6527574e9a128e4f5d60774824b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2944646
Auto-Submit: Brian Ryner <bryner@google.com>
Commit-Queue: Dirk Pranke <dpranke@google.com>
Reviewed-by: Dirk Pranke <dpranke@google.com>

bootstrap/manifest_bleeding_edge.txt

@@ -18,10 +18,10 @@
 $VerifiedPlatform windows-386 windows-amd64 linux-amd64 mac-amd64
 
 @Subdir python
-infra/3pp/tools/cpython/${platform} version:2@2.7.18.chromium.37
+infra/3pp/tools/cpython/${platform} version:2@2.7.18.chromium.39
 
 @Subdir python3
-infra/3pp/tools/cpython3/${platform} version:2@3.8.10.chromium.17
+infra/3pp/tools/cpython3/${platform} version:2@3.8.10.chromium.19
 
 @Subdir git
 infra/3pp/tools/git/${os}-${arch} version:2@2.30.2.chromium.6