;doc: simplify new bug template

.github/ISSUE_TEMPLATE/a-bug.md

@@ -4,40 +4,9 @@ about: A weakness in the software, documentation, usability, or project
 labels: A BUG
 ---
 
-Thanks for reporting! Here are some tips (please delete them before submitting):
+Thanks for reporting! Here are some tips, please remove this text before submitting:
 
-- Have you checked the hledger manuals, and the right version ?
-  Eg for `hledger`: run `hledger help`, or go to
-  https://hledger.org/hledger.html and select your version at the top.
-
-- If you're not sure this is a bug, or if some discussion would help,
-  contact us on chat or the mail list first:
-  https://hledger.org/support.html
-
-- Not required, but any of these can help get issues resolved faster:
-  - A small reproducible example
-  - The output of hledger --version
-  - What platform you're on
-  - Links to any related docs that you found
-
-- If you have the access level to set labels, consider adding
-  - Any topic labels that seem appropriate
-  - Severity and impact labels estimating 
-
-    - How severe is this bug ?
-
-      - severity5: Data loss or privacy/security loss. A user would drop the product.
-      - severity4: Crash or bothersome regression or major usability or documentation issue. A user may look for an alternative product.
-      - severity3: Installability, packaging or new user experience issue. A potential user would fail to get started.
-      - severity2: Minor/moderate usability/doc issue. Easy to avoid or not a big deal.
-      - severity1: Cleanup/design/developer issue. Significant only to developers and design-minded users.
-
-    - Who is likely to be impacted by this bug ?
-
-      - impact5: All users.
-      - impact4: Most users.
-      - impact3: A minority of users.
-      - impact2: Only packagers or developers.
-      - impact1: Almost no one.
-
-(These are now in the issue tracker as severityN and impactN labels, keep synced.)
+- Have you checked (the right version of) the manual ? Eg https://hledger.org/hledger.html
+- If some discussion would help, just ask in chat or mail list: https://hledger.org/support.html
+- Any of these are very helpful: a small reproducible example, hledger --version output,
+  what platform you're running on, a link to to any relevant doc that you found.