Update meta data of docs

docs/contributing/guidelines-backend.md

@@ -1,6 +1,5 @@
 ---
 date: "2021-11-01T23:41:00+08:00"
-title: "Guidelines for Backend Development"
 slug: "guidelines-backend"
 sidebar_position: 20
 aliases:

docs/contributing/guidelines-refactoring.md

@@ -1,6 +1,5 @@
 ---
 date: "2023-02-14T00:00:00+00:00"
-title: "Guidelines for Refactoring"
 slug: "guidelines-refactoring"
 sidebar_position: 40
 aliases:

docs/contributing/localization.md

@@ -1,6 +1,5 @@
 ---
 date: "2016-12-01T16:00:00+02:00"
-title: "Localization"
 slug: "localization"
 sidebar_position: 70
 aliases: