add missing args.architecture to _check_fuzzer_exists

[shafouz]

Adds args.architecture to _check_fuzzer_exists calls. Without this when you run on aarch64 python3 infra/helper.py run_fuzzer <...> it pulls the x86_64 image and gives a exec format error.

[google-cla[bot]]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[jonathanmetzman]

Can you sign the CLA?

[shafouz]

Can you sign the CLA?

i did

[jonathanmetzman]

Sorry for the long delay in merging this