Make Edits proposed by SquidDev-CC (#65)

* Use toolchains as proposed by SquidDev-CC

* Removed jcenter() repo (where bad mercury dep was coming from)

Co-authored-by: ToadDev <748280+Toad-Dev@users.noreply.github.com>

build.gradle

@@ -5,8 +5,12 @@ plugins {
     id "com.github.hierynomus.license" version "0.15.0"
 }
 
-sourceCompatibility = JavaVersion.VERSION_1_8
-targetCompatibility = JavaVersion.VERSION_1_8
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(8)
+        vendor = JvmVendorSpec.ADOPTOPENJDK
+    }
+}
 
 version = mod_version