Update gradle, move maven repo to project gradle file (#1097)

I would also like to remove `jcenter()` but right now two repositories are using it.

`com.pes.materialcolorpicker:library` `com.amulyakhare:com.amulyakhare.textdrawable`

Co-authored-by: M M Arif <mmarif@swatian.com>
Reviewed-on: https://codeberg.org/gitnex/GitNex/pulls/1097

app/build.gradle

@@ -37,18 +37,14 @@ android {
     compileOptions {
         coreLibraryDesugaringEnabled true
 
-        sourceCompatibility JavaVersion.VERSION_1_8
-        targetCompatibility JavaVersion.VERSION_1_8
+        sourceCompatibility JavaVersion.VERSION_11
+        targetCompatibility JavaVersion.VERSION_11
     }
     defaultConfig{
         vectorDrawables.useSupportLibrary = true
     }
 }
 
-repositories {
-    mavenCentral()
-}
-
 configurations {
     cleanedAnnotations
     compile.exclude group: 'org.jetbrains', module: 'annotations'

build.gradle

@@ -4,10 +4,11 @@ buildscript {
 
     repositories {
         google()
+        mavenCentral()
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:7.0.0'
+        classpath 'com.android.tools.build:gradle:7.1.2'
 
     }
 }
@@ -15,6 +16,7 @@ buildscript {
 allprojects {
     repositories {
         google()
+        mavenCentral()
         jcenter()
         maven { url 'https://jitpack.io' }
     }