Bug reporting: Replace "Windows" with "Generic" (openSUSE#196)

As we don't support Windows, it's not of real use for us.
Additionally, a "Generic" keyword is useful when no specific
OS is needed.

Author: tomschr

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -39,8 +39,8 @@ body:
       multiple: true
       options:
         - Linux
-        - Windows
         - macOS
+        - Generic
         - Other (describe below)
     validations:
       required: true

changelog.d/196.infra.rst

@@ -0,0 +1 @@
+In the bug reporting template, remove "Windows" and add "Generic".