build: remove jitpack from buildscript repos

Not needed for plugins

Signed-off-by: Álvaro Brey <alvaro.brey@nextcloud.com>

build.gradle

@@ -31,7 +31,6 @@ buildscript {
         google()
         gradlePluginPortal()
         mavenCentral()
-        maven { url 'https://jitpack.io' }
     }
 
     dependencies {