Update .spi.yml (#14)

- I don't think we want to publish docs for the internal macro code.
  - I think we should try building on Swift 5.8 to see if the APIs stop
    showing up as "deprecated" by default.

.spi.yml

@@ -1,7 +1,5 @@
 version: 1
 builder:
   configs:
-  - documentation_targets:
-    - Perception
-    - PerceptionMacros
-    swift_version: 5.9
+  - documentation_targets: [Perception]
+    swift_version: 5.8