Add gtest-parallel to manifest

This repo is a new dependency of ChromeOS unit tests. After updating
ChromeOS build tools, our BE step that runs ebuild unit tests fails if
this repo is missing.

BUG=b/307995090
TEST=repo init and sync
RELEASE_NOTE=None

Change-Id: I5756e32d56bd28b678d09f97d5beecbb2d2e4d71
Reviewed-on: https://cos-review.googlesource.com/c/cos/manifest/+/63723
Reviewed-by: He Gao <hegao@google.com>
Tested-by: Robert Kolchmeyer <rkolchmeyer@google.com>
diff --git a/external_full.xml b/external_full.xml
index 529286c..23cf3c4 100644
--- a/external_full.xml
+++ b/external_full.xml
@@ -80,6 +80,9 @@
            revision="e7b8e288b01a667dba87d7d2c584b950adb6200c" >
              <linkfile src="workspace_root/MODULE.bazel" dest="src/MODULE.bazel" />
   </project>
+  <project path="src/third_party/gtest-parallel"
+           name="mirrors/github.com/google/gtest-parallel"
+           revision="96f4f904922f9bf66689e749c40f314845baaac8" />
 
   <!-- COS sources -->
   <project path="src/overlays"