Clean up formatting of Observable macro

[stephencelis]

Currently the macro preserves some trivia it shouldn't, and has inconsistent indentation. This PR trims this trivia and leaves things unindented so that SwiftSyntax's formatter can take care of it.

[stephencelis]

Before/after:

 class State {
   var count = 0 {
-    @storageRestrictions(initializes: _count )
+    @storageRestrictions(initializes: _count)
       init(initialValue) {
-        _count  = initialValue
+        _count = initialValue
       }
       get {
-        access(keyPath: \.count )
-        return _count 
+        access(keyPath: \.count)
+        return _count
       }
       set {
-        withMutation(keyPath: \.count ) {
-          _count  = newValue
+        withMutation(keyPath: \.count) {
+          _count = newValue
         }
       }
     }
   }
   …
   internal nonisolated func access<Member>(
-      keyPath: KeyPath<State , Member>
+    keyPath: KeyPath<State, Member>
   ) {
     _$observationRegistrar.access(self, keyPath: keyPath)
   }
   …
 }

[phausler]

Thanks for cleaning this up! the output looks great.

From what I can tell this is a non-functional change so I don't see any issues with it.

[phausler]

@swift-ci please smoke test

[DougGregor]

Thank you!