Hide SoC-2019 under the historical materials

Author: chriscool

SoC-2019-Ideas.md

@@ -1,6 +1,7 @@
 ---
 layout: default
 title: SoC 2019 Ideas
+navbar: false
 ---
 
 This is the idea page for Summer of Code 2019 for Git.

SoC-2019-Microprojects.md

@@ -1,6 +1,7 @@
 ---
 layout: default
 title: SoC 2019 Applicant Microprojects
+navbar: false
 ---
 
 ## Introduction

SoC-2019-Org-Application.md

@@ -1,6 +1,7 @@
 ---
 layout: default
 title: SoC 2019 Organization Application
+navbar: false
 ---
 
 This is a draft of git's application to Google's Summer of Code 2019.