workflows/pull-request-target: increase retries for prepare step

We still get plenty of errors in the prepare step for the diff requests
to take way too long - let's increase the number of retries massively
now. These are repeated with exponential backoff, so hopefully they will
succeed with some cooldown, when GitHub had time to compute the right
diff in the background.

(cherry picked from commit 436876e070)

.github/workflows/pull-request-target.yml

@@ -45,7 +45,7 @@ jobs:
       - id: prepare
         uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
         with:
-          retries: 3
+          retries: 10
           # The default for this includes code 422, which happens regularly for us when comparing commits:
           #   422 - Server Error: Sorry, this diff is taking too long to generate.
           # Listing all other values from here to effectively remove 422:

.github/workflows/test.yml

@@ -28,7 +28,12 @@ jobs:
       - id: prepare
         uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
         with:
-          retries: 3
+          retries: 10
+          # The default for this includes code 422, which happens regularly for us when comparing commits:
+          #   422 - Server Error: Sorry, this diff is taking too long to generate.
+          # Listing all other values from here to effectively remove 422:
+          #   https://github.com/octokit/plugin-retry.js/blob/9a2443746c350b3beedec35cf26e197ea318a261/src/index.ts#L14
+          retry-exempt-status-codes: 400,401,403,404
           script: |
             require('./ci/github-script/prepare.js')({
               github,