Roll depot_tools cpython3 version.

See https://chromium.googlesource.com/chromium/tools/depot_tools/+/e77e3c879a3f795161d3efa096c9caa33c7a0c2b

Bug: 1175200
Change-Id: I340be41bd2c7e796de5d153b95873e4b45e5280e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2879116
Commit-Queue: Brian Ryner <bryner@google.com>
Reviewed-by: Dirk Pranke <dpranke@google.com>

bootstrap/manifest.txt

@@ -21,7 +21,7 @@ $VerifiedPlatform windows-amd64 linux-amd64 mac-amd64
 infra/3pp/tools/cpython/${platform} version:2@2.7.18.chromium.35
 
 @Subdir python3
-infra/3pp/tools/cpython3/${platform} version:2@3.8.9.chromium.14
+infra/3pp/tools/cpython3/${platform} version:2@3.8.10.chromium.17
 
 # TODO(https://crbug.com/1184766): Remove `=amd64` once mac/arm64 git exists
 @Subdir git