fix: small typo in error (#2853)

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This is just a small typo fix. 
Working on a fix for
snakemake/snakemake-executor-plugin-kubernetes#19
and eventually ended up at the following error when deploying to
kubernetes:
```
Error: Error when applying default storage provider gcs to upload workflow sources. {query_validity}
```
Fixing this here so the error is more clear since it looks like
kubernetes uses the docker container from main.

snakemake/api.py

@@ -209,7 +209,7 @@ def deploy_sources(
             raise ApiError(
                 f"Error when applying default storage provider "
                 f"{storage_settings.default_storage_provider} to upload workflow "
-                "sources. {query_validity}"
+                f"sources. {query_validity}"
             )
         storage_object = provider_instance.object(query)
         async_run(storage_object.managed_retrieve())