pull_request_template: improvements based on webhook

Since the formality checks are now automated via the webhook, contributors
no longer need to manually go through a checklist. The bot will flag any
issues, request fixes, and apply a label indicating that requirements are
not met. Once all issues are resolved, the label is automatically removed.

This also benefits maintainers during review, as the previous manual
checklist could be skipped or filled with inaccurate information.

Remove the checklist items that are now automatically enforced and keep
only the ones that are not yet automated and still make sense to have.

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>

.github/pull_request_template.md

@@ -58,9 +58,5 @@ MAY:
 ## Checklist
 <!-- Place an x inside each [ ] and remove the empty space to check each item off the list. 
 They should look like this: [x], otherwise leave them as is. -->
-- [ ] This PR is not from my *main* or *master* branch :poop:, but a *separate* branch. :white_check_mark:
-- [ ] Each commit has a valid :black_nib: `Signed-off-by: <my@email.address>` row (via `git commit --signoff`).
-- [ ] Each commit and PR title has a valid :memo: `<package name>: title` first line subject for packages.
-- [ ] Incremented :up: any `PKG_VERSION` in the Makefile.
-- [ ] _(Optional)_ Includes what Issue it closes (e.g. openwrt/luci#issue-number).
-- [ ] _(Optional)_ Includes what it depends on (e.g. openwrt/packages#pr-number in sister repo).
+- [ ] _(Nice to have)_ Includes what Issue it closes (e.g. openwrt/luci#issue-number).
+- [ ] _(Nice to have)_ Includes what it depends on (e.g. openwrt/packages#pr-number in sister repo).