Bug 1486004 - Part 3 - change help prompt for remote test root to show /data/local/tmp/test_root, r=gbrown

Depends on D82745

Differential Revision: https://phabricator.services.mozilla.com/D82746

python/mozbuild/mozbuild/mach_commands.py

@@ -464,7 +464,7 @@ class GTestCommands(MachCommandBase):
                      dest='remote_test_root',
                      group='Android',
                      help='Remote directory to use as test root '
-                     '(eg. /mnt/sdcard/tests or /data/local/tests).')
+                     '(eg. /data/local/tmp/test_root).')
     @CommandArgument('--libxul',
                      dest='libxul_path',
                      group='Android',