chore: switch bug template to "expected/actual" behavior (aws#9423)

Bug reports typically result from a distinction between a user's mental model and actual behavior.

To bring this to the front and center, I like the phrasing:

* Tell me what you expected to happen
* Tell me what actually happened

More than the current:

* Paste code
* See error

The new phrasing subsumes the old one (what actually happened? I got an error) while also allowing to catch more bug-like scenarios.

Hopefully it will prevent incomplete reports like this: aws#9270 where the user pasted in the code, didn't get an error so didn't fill out the "error" section, and didn't really state what they expected or saw happen.


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.github/ISSUE_TEMPLATE/bug.md

@@ -18,16 +18,17 @@ description of the bug:
 minimal amount of code that causes the bug (if possible) or a reference:
 -->
 
-
-
-
-### Error Log
+### What did you expect to happen?
 
 <!--
-what is the error message you are seeing?
+What were you trying to achieve by performing the steps above?
 -->
 
+### What actually happened?
 
+<!--
+What is the unexpected behavior you were seeing? If you got an error, paste it here.
+-->
 
 
 ### Environment