Remove mistakenly added Hfest'23 in Past Events

_Sidebar.md

@@ -8,6 +8,7 @@
     * [[UX researchers|Conducting-research-with-students]]
     * [[Voice artists | Instructions-for-voice-artists]]
     * [[Designers and artists|Contributing-to-Oppia's-design]]
+  * **[[Hacktoberfest 2023|Hacktoberfest-2023]]**
   * **[[Google Summer of Code 2023|Google-Summer-of-Code-2023]]**
 ---
 **Developing Oppia**
@@ -128,7 +129,7 @@
     * [[Wiki-style-guide|Wiki-style-guide]]
   * Past Events
     * Google Summer of Code: [[2022|Google-Summer-of-Code-2022]], [[2021|Google-Summer-of-Code-2021]], [[2020|Google-Summer-of-Code-2020]], [[2019|Google-Summer-of-Code-2019]], [[2018|Google-Summer-of-Code-2018]], [[2017|Google-Summer-of-Code-2017]], [[2016|Google-Summer-of-Code-2016]]
-    * Hacktoberfest: [[2023|Hacktoberfest-2023]], [[2022|Hacktoberfest-2022]], [[2021|Hacktoberfest-2021]], [[2020|Hacktoberfest-2020]], [[2019|Hacktoberfest-2019]], [[2018|Hacktoberfest-2018]], [[2017|Hacktoberfest-2017]], [[2016|Hacktoberfest-2016]]
+    * Hacktoberfest: [[2022|Hacktoberfest-2022]], [[2021|Hacktoberfest-2021]], [[2020|Hacktoberfest-2020]], [[2019|Hacktoberfest-2019]], [[2018|Hacktoberfest-2018]], [[2017|Hacktoberfest-2017]], [[2016|Hacktoberfest-2016]]
     * GHC Open Source Day: [[2019|GHC-Open-Source-Day-2019]], [[2018|GHC-Open-Source-Day]]
     * Season of Docs: [[2019|Season-of-Docs-2019]]
     * DSC-SLoP (Semester Long Project): [[2022|SLoP-2022]], [[2020|SLoP-2020]]