docs: tweak structure of permission docs

Signed-off-by: MT Lewis <mtlewis@users.noreply.github.com>

docs/permission/concepts.md

@@ -1,6 +1,6 @@
 ---
 id: concepts
-title: Permission Framework Concepts
+title: Concepts
 description: A list of important permission framework concepts
 ---
 

docs/permission/overview.md

@@ -1,6 +1,6 @@
 ---
 id: overview
-title: Permission Framework Overview
+title: Overview
 description: A high level overview of the Backstage permission framework
 ---
 

microsite/sidebars.json

@@ -263,9 +263,9 @@
     ],
     "Permissions": [
       "permission/overview",
+      "permission/concepts",
       "permission/getting-started",
       "permission/writing-a-policy",
-      "permission/concepts",
       {
         "type": "subcategory",
         "label": "Permission framework for plugin authors",