Upgrade to gh-aw v0.71.5 (bundle transport for merge commits)

v0.71.5 includes #30287: push_to_pull_request_branch auto-switches
to bundle transport when merge commits are detected, fixing the
empty-patch and conflict failures that blocked Evergreen from
merging main into PR branches.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mrjf

.github/aw/actions-lock.json

@@ -10,15 +10,15 @@
       "version": "v9.0.0",
       "sha": "3a2844b7e9c422d3c10d287c895573f7108da1b3"
     },
-    "github/gh-aw-actions/setup@v0.71.4": {
-      "repo": "github/gh-aw-actions/setup",
-      "version": "v0.71.4",
-      "sha": "f8495a686e66770ae977f82732f34d7340ee42a4"
-    },
     "github/gh-aw/actions/setup@v0.71.4": {
       "repo": "github/gh-aw/actions/setup",
       "version": "v0.71.4",
       "sha": "ff0acb2ee8535c83a40653e363362aa0354f3407"
+    },
+    "github/gh-aw/actions/setup@v0.71.5": {
+      "repo": "github/gh-aw/actions/setup",
+      "version": "v0.71.5",
+      "sha": "19ac811a4a85389c33b15128e1d7b7d4507f814a"
     }
   }
 }