remove erroneous mount entry from fly.toml (#2644)

Fly CLI complains about the duplicate `mount` entry to `fly.toml`,
failing the build

### Change Type

- [x] `internal` — Any other changes that don't affect the published
package

apps/huppy/fly.toml

@@ -2,7 +2,6 @@
 app = "tldraw-repo-sync"
 kill_signal = "SIGINT"
 kill_timeout = 5
-mounts = []
 primary_region = "lhr"
 processes = []