CocoaSpice: disable GPU bliting due to performance issues

On non-Apple Silicon Macs, the bandwidth of a large number of display
updates when the GPU is under load leads to bad tearing. By moving back to
CPU bliting, we are able to reduce the bandwidth at the cost of extra CPU
work.

Fixes #5049

UTM.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -15,7 +15,7 @@
       "location" : "https://github.com/utmapp/CocoaSpice.git",
       "state" : {
         "branch" : "main",
-        "revision" : "40a558658b142f63a012e62abcac4dd1aaa719f0"
+        "revision" : "eca498d69cbe67e1e2dd9228135f4cdbfdec1ea3"
       }
     },
     {