refactor: Remove functions_concepts_after_response

[grant]

Removes functions_concepts_after_response.

This is not a useful GCF function, does not have a test, and does not have a strong reason to keep for N languages. Only implemented in Node right now.

samples/596
Doc: https://cloud.google.com/functions/docs/concepts/exec#function_execution_timeline

[ace-n]

Personally I think that we should keep this (since it's useful for explaining the related concept), but I'll defer to @labtopia

[labtopia]

This may not be the very best sample we could have had here, but I think the underlying concept is important, and the sample does illustrate it. Further, this doesn't seem like a case where we need a sample for every runtime. A single sample illustrating the concept is sufficient. I think the section would be a lot weaker without the sample. Therefore, I am not in favor of removing it.

[grant]

I'd rather have the one place in our docs have something shorter so the reader doesn't need to read the whole sample:

res.end();

// This statement may not execute
console.log('Function complete!');

What about moving the region tags to just show this (above)?

[ace-n]

Middle ground - how about we exclude the JSDoc comment with the region tags, to clearly delineate that this code is (still) within a function?

[grant]

Closing due to lack of interest in changing this sample.