ci: Disable duckdb tests while caching has issues #7968

Job	Run time
build-prqlc (ubuntu-latest, x86_64-unknown-linux-musl)	2m 58s
build-prqlc (macos-latest, x86_64-apple-darwin, test-dbs)	5m 48s
build-prqlc (windows-latest, x86_64-pc-windows-msvc)	5m 49s
check-links-markdown	15s
nightly	0s
publish-web	0s
test-all	0s
automerge-dependabot	0s
test-rust (ubuntu-latest, wasm32-unknown-unknown) / test-rust	4m 31s
test-rust (ubuntu-latest, x86_64-unknown-linux-gnu) / test-rust	7m 24s
check-links-book / changes	4s
lint-megalinter / lint-megalinter	4m 36s
check-links-book / check	0s
check-ok-to-merge	2s
	31m 27s

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