Fix gn_migration.gypi after https://codereview.chromium.org/1231283003/

Without this, building 'all' won't create the isolate file, making the isolate
step after the compile step fail.

BUG=98637
TBR=maruel

Review URL: https://codereview.chromium.org/1244443002

Cr-Original-Commit-Position: refs/heads/master@{#339079}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 4681b9749b14de949120cb7e2090255dd395b433

gn_migration.gypi

@@ -544,6 +544,7 @@
             '../sql/sql.gyp:sql_unittests_run',
             '../sync/sync.gyp:sync_unit_tests_run',
             '../third_party/cacheinvalidation/cacheinvalidation.gyp:cacheinvalidation_unittests_run',
+            '../third_party/mojo/mojo_edk_tests.gyp:mojo_public_bindings_unittests_run',
             '../tools/gn/gn.gyp:gn_unittests_run',
             '../ui/accessibility/accessibility.gyp:accessibility_unittests_run',
             '../ui/app_list/app_list.gyp:app_list_unittests_run',