cpython3 3.8.10.chromium.21 to depot_tools bleeding_edge.

Bug: 1230447
Change-Id: I7cfacab0fd09d57ba41c8df87b072733bc1fe35a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3146215
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

@@ -21,7 +21,7 @@ $VerifiedPlatform windows-386 windows-amd64 linux-amd64 mac-amd64 mac-arm64
 infra/3pp/tools/cpython/${platform} version:2@2.7.18.chromium.39
 
 @Subdir python3
-infra/3pp/tools/cpython3/${platform} version:2@3.8.10.chromium.20
+infra/3pp/tools/cpython3/${platform} version:2@3.8.10.chromium.21
 
 @Subdir git
 infra/3pp/tools/git/${platform} version:2@2.33.0.chromium.6