.github: Remove automated bug report template for now

There were some problems with it, so github didn't even use it. Remove it for
now, so the old template works again.

.github/ISSUE_TEMPLATE/mu4e-bug-report.yml

@@ -1,77 +0,0 @@
-name: Mu4e Bug Report
-description: File a bug report
-labels: ["bug"]
-body:
-  - type: markdown
-    attributes:
-      value: |
-        Thanks for taking the time to fill out this bug report!
-  - type: textarea
-    id: what-happened
-    attributes:
-      label: What happened?
-      description: Also tell us, what did you expect to happen?
-      placeholder: Tell us what you see!
-    validations:
-      required: true
-  - type: textarea
-    id: recipe
-    attributes:
-      label: How to reproduce?
-      description: Tell us how to reproduce bug step by step?
-      placeholder: Detailed steps to reproduce the behavior. If this is about a specific (kind of) message, **always** attach an (anonymized as need) example message.
-    validations:
-      required: true
-  - type: dropdown
-    id: Emacs-version
-    attributes:
-      label: Emacs Version
-      description: What version of Emacs are you running?
-      options:
-        - Emacs-25*
-        - Emacs-26*
-        - Emacs-26.3
-        - Emacs-27.1
-        - Emacs-27.2
-        - Emacs-28.0.50
-    validations:
-      required: true
-  - type: dropdown
-    id: Platform
-    attributes:
-      label: OS
-      description: What OS are you running on?
-      options:
-        - GNU/Linux
-        - Freebsd
-        - MacOSX
-        - Windows
-        - Other
-    validations:
-      required: true
-  - type: checkboxes
-    id: terms
-    attributes:
-      label: Minimal configuration
-      description: you are running vanilla emacs (i.e. without Doom, Evil, Spacemacs etc.) (otherwise, please try to reproduce without those.
-      options:
-        - label: I agree using a minimal configuration 
-          required: true
-
-  - type: checkboxes
-    id: terms
-    attributes:
-      label: Minimal configuration
-      description: you are running mu4e without any third-party extensions (otherwise, please try to reproduce without those).
-      options:
-        - label: I agree not using third party extensions
-          required: true
-
-  - type: checkboxes
-    id: terms
-    attributes:
-      label: Minimal configuration
-      description: you are running either the latest 1.6.x release, or a 1.7.x development release (otherwise, please upgrade).
-      options:
-        - label: I agree not using third party extensions
-          required: true