Fix gradleutils.unpack being inaccessible

Was previously a static method but static methods are not passed down
from inherited interfaces to the implementation classes. At least not
for Groovy objects(?) Static fields continue to work though. Super
weird.

Author: Jonathing

src/main/groovy/net/minecraftforge/gradleutils/GradleUtilsExtension.java

@@ -272,11 +272,11 @@ default Action<MavenArtifactRepository> getPublishingForgeMaven(Provider<?> defa
 
     /* MISCELLANEOUS */
 
-    static <T> T unpack(Provider<T> value) {
+    default <T> T unpack(Provider<T> value) {
         return value.get();
     }
 
-    static <T> T unpack(ProviderConvertible<T> value) {
+    default <T> T unpack(ProviderConvertible<T> value) {
         return unpack(value.asProvider());
     }
 }