Fix matrix setup, references

Author: andrewdmontgomery

.buildkite/pipeline.yml

@@ -21,22 +21,22 @@ steps:
   #################
   # Build and Test
   #################
-  - label: "📦 Build and Test Swift Package ({{matrix}})"
+  - label: "📦 Build and Test Swift Package ({{matrix.image_id}})"
     key: "test"
     command: |
       validate_swift_package device:"{{matrix.device}}"
     plugins: [$CI_TOOLKIT]
     env:
-      IMAGE_ID: "{{matrix}}"
+      IMAGE_ID: "{{matrix.image_id}}"
     matrix:
       setup:
-        image:
+        image_id:
           - $IMAGE_ID
         device:
           - "iPhone SE (3rd generation) (17.5)"
       adjustments:
         - with:
-          image: "xcode-15.1"
+          image_id: "xcode-15.1"
           device: "iPhone SE (3rd generation) (17.2)"
 
   ###################