change java version to 8

Author: frost13it

build.gradle

@@ -4,7 +4,7 @@ plugins {
 }
 
 ext {
-    release = '1.3'
+    release = '1.3.1'
 
     versions = [
         assertj: '3.14.0',
@@ -18,7 +18,7 @@ ext {
 group = "ru.kontur.kinfra"
 version = ext.version
 
-sourceCompatibility = 11
+sourceCompatibility = 8
 
 dependencies {
     testImplementation "org.assertj:assertj-core:${versions.assertj}"