fix(functions): fix invalid region tag

[iennae]

making sure this sample includes a valid region tag; it could be that this sample needs to be archived but in case it's in use within the repo for testing, making sure it's associated with the right region tag. Additionally, the region tag may need to change in the near future and this will make it more discoverable that it needs to be updated. Also recognize that functions_ is what's in the configuration, but functions is in broader use and cloudfunctions is the appropriate one.

[snippet-bot]

Here is the summary of possible violations 😱

There is a possible violation for not having product prefix.

• packages/google-cloud-functions/samples/quickstart.js:17, tag cloudfunctions_nodejs_quickstart

The end of the violation section. All the stuff below is FYI purposes only.

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Here is the summary of changes.

You are about to add 1 region tag.

• packages/google-cloud-functions/samples/quickstart.js:17, tag cloudfunctions_nodejs_quickstart

You are about to delete 1 region tag.

• packages/google-cloud-functions/samples/quickstart.js:17, tag cloud_nodejs_functions_quickstart

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[iennae]

I made a very small change, and I'm very unclear why owlbot made a bunch of changes to other files that I didn't change.