docs/releases: Fix warning "document isn't included in any toctree"

While running Sphinx, it shows the warning "document isn't included in
any toctree" for the documents checklist.md and templates.md. These are
not meant to be listed in ToC trees.

Thus, mark them as orphaned to exclude them from ToC trees.

Change-Id: I1ff8f7c24ac9b3c3a120914c0c72ab73e85c4873
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62584
Reviewed-by: Thomas Heijligen <src@posteo.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/releases/checklist.md

@@ -1,3 +1,7 @@
+```eval_rst
+:orphan:
+```
+
 # coreboot Release Process
 
 This document describes our release process and all prerequisites to implement

Documentation/releases/templates.md

@@ -1,3 +1,7 @@
+```eval_rst
+:orphan:
+```
+
 # Communication templates related to release management
 
 ## Deprecation notices