Temporarily disable penny-bot while we investigate the failure

This is currently failing, presumably due to a package visibility
change:
```
swift-source-compat-suite/project_cache/penny-bot/Lambdas/GitHubAPI/GeneratedSources/Types.swift:1147:59: error: initializer 'init(per_page:page:)' is package and cannot be referenced from a default argument value
 1145 |     package func pulls_list_files(
 1146 |         path: Operations.pulls_list_files.Input.Path,
 1147 |         query: Operations.pulls_list_files.Input.Query = .init(),
      |                                                           `- error: initializer 'init(per_page:page:)' is package and cannot be referenced from a default argument value
 1148 |         headers: Operations.pulls_list_files.Input.Headers = .init()
 1149 |     ) async throws -> Operations.pulls_list_files.Output {
      :
30245 |                 ///   - per_page: The number of results per page (max 100).
```

Temporarily disable while we look into it.

Author: bnbarham

projects.json

@@ -4767,7 +4767,14 @@
       },
       {
         "action": "TestSwiftPackage"
-      }
+      },
+        "xfail": [
+          {
+            "issue": "rdar://128175704",
+            "branch": ["main"],
+            "job": ["source-compat"]
+          }
+        ]
     ]
   },{
     "repository": "Git",