Fix crash when running CI builds

Removed 'GDScriptNativeClass', 'JNISingleton', and 'JavaClass' entries from the disabled classes list.

Author: syntaxerror247

.github/disabled_classes.gdbuild

@@ -62,7 +62,6 @@
 		"FramebufferCacheRD",
 		"GDExtension",
 		"GDExtensionManager",
-		"GDScriptNativeClass",
 		"GLTFAccessor",
 		"GLTFAnimation",
 		"GLTFBufferView",
@@ -96,11 +95,7 @@
 		"ImageFormatLoader",
 		"ImporterMesh",
 		"InstancePlaceholder",
-		"JNISingleton",
 		"JSONRPC",
-		"JavaClass",
-		"JavaClassWrapper",
-		"JavaObject",
 		"JointLimitation3D",
 		"KinematicCollision2D",
 		"KinematicCollision3D",