Update index.mdx

Author: tustanivsky

docs/platforms/unreal/configuration/debug-symbols/index.mdx

@@ -31,6 +31,12 @@ The `sentry-cli` require you to specify the organization and project to work wit
 
 To configure the `sentry-cli` using properties file enter the [Auth Token](https://sentry.io/orgredirect/organizations/:orgslug/settings/auth-tokens/), Organization Slug, and Project Name. Note, that the Unreal Engine SDK automatically creates a `sentry.properties` file at the root of your project directory to store the configuration. This configuration file should **never** be made publicly available.
 
+<Alert>
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+If the properties file is not found during the symbol upload process, it falls back to using environment variables.
+
+</Alert>
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 ### Environment Variables
 
 The `sentry-cli` can be configured by setting the following environment variables which will be automatically picked up during the debug symbol upload: