Modernize GitHub pull-request template (#70787)

Change:
- Remove "New Module Pull Request" since we're not taking new modules in
  ansible/ansible
- Add "Tests Pull Request" to use for things like adding coverage that
  aren't bugfixes.

Signed-off-by: Rick Elrod <rick@elrod.me>

.github/PULL_REQUEST_TEMPLATE.md

@@ -8,7 +8,7 @@
 - Bugfix Pull Request
 - Docs Pull Request
 - Feature Pull Request
-- New Module Pull Request
+- Test Pull Request
 
 ##### COMPONENT NAME
 <!--- Write the short name of the module, plugin, task or feature below -->