gn2bp: Use python3 for jni_registration_generator.py

Test: ./update_results.sh
Change-Id: If3d694d32b3396404b48e045c7a6163d934f8129
diff --git a/tools/gn2bp/Android.bp.swp b/tools/gn2bp/Android.bp.swp
index e13e2f8..247d896 100644
--- a/tools/gn2bp/Android.bp.swp
+++ b/tools/gn2bp/Android.bp.swp
@@ -1968,7 +1968,7 @@
          "do " +
          "echo \"../$$current_dir/$$f\" >> $(genDir)/java.sources; " +
          "done; " +
-         "$(location base/android/jni_generator/jni_registration_generator.py) --srcjar-path " +
+         "python3 $(location base/android/jni_generator/jni_registration_generator.py) --srcjar-path " +
          "$(genDir)/components/cronet/android/cronet_jni_registration.srcjar " +
          "--depfile " +
          "$(genDir)/components/cronet/android/cronet_jni_registration.d " +