Remove Issue template

[fabianfett]

Expected behavior

That issue template is way to verbose. Let's just remove it.

Actual behavior

N/A

Steps to reproduce

N/A

If possible, minimal yet complete reproducer code (or URL to code)

No response

What version of this project (swift-aws-lambda-runtime) are you using?

N/A

Swift version

N/A

Amazon Linux 2 docker image version

No response

[sebsto]

Actually, It gets in the way for us when we use the issue system as our todo list. But it obliges users to be detailed in their description. (see #449 as a good example)

Closing this for now.