Re-run the CI build

.ci-builds/.azure-pipelines-icu4c.yml

@@ -572,11 +572,11 @@ jobs:
     - task: Cache@2
       displayName: 'Restore Cygwin cache'
       inputs:
-        # Use the contents of the file ".azure-pipelines.yml" as part of the key, as that contains the list of CYG_PACKAGES.
+        # Use the contents of the file ".azure-pipelines-icu4c.yml" as part of the key, as that contains the list of CYG_PACKAGES.
         # Also include the Cygwin version as part of the key. If we want to use a newer version of Cygwin, we can update CYG_VERSION_KEY.
         # Note: CYG_VERSION_KEY may become out of sync with (older than) the version we actually use if we update this file
         #       without updating CYG_VERSION_KEY. Any updates to this file guarantees that we're using the latest version.
-        key: '"$(CYG_VERSION_KEY)" | .ci-builds/.azure-pipelines.yml'
+        key: '"$(CYG_VERSION_KEY)" | .ci-builds/.azure-pipelines-icu4c.yml'
         path: "$(CYG_CACHE)"
     - task: PowerShell@2
       displayName: 'Download Cygwin setup'