Fix flakes in ./topdown/cache #11278

Job	Run time
Generate Code	1m 7s
YAML Lint	19s
Rego PR checks	1m 33s
Go Lint	2m 3s
Check Generated	26s
Go compat build/test (ubuntu-22.04, 1.21)	3m 20s
Go Test (linux)	4m 48s
Go Build (linux amd64)	2m 23s
Go compat build/test (macos-14, 1.21)	4m 46s
Go Test (darwin)	4m 52s
Go Race Detector	5m 50s
Go Build (linux arm64)	2m 7s
Go Build (linux arm64GO_TAGS="-tags=opa_no_oci")	2m 4s
WASM	8s
Go Build (windows amd64)	2m 30s
Go Build (darwin amd64)	2m 53s
Go Build (darwin arm64)	52s
docker image smoke test	44s
smoke-test-binaries (linux, ubuntu-22.04, opa_linux_amd64, amd64)	10s
smoke-test-binaries (linux, ubuntu-22.04, opa_linux_amd64_static, amd64, disabled)	15s
smoke-test-binaries (darwin, macos-13, opa_darwin_amd64, amd64)	24s
smoke-test-binaries (darwin, macos-14, opa_darwin_arm64_static, arm64, disabled)	17s
smoke-test-binaries (windows, windows-latest, opa_windows_amd64.exe, amd64)	1m 3s
	44m 54s

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