Fix permissions of docker workflow #4216

Job	Run time
Build & test (plutus-cbor)	1m 34s
Build & test (plutus-merkle-tree)	1m 35s
Build & test (hydra-plutus)	1m 39s
Build haddock using nix	1m 22s
Build & test (hydra-tui)	2m 29s
Build & test (hydra-node)	4m 31s
Build & test (hydra-cluster)	7m 48s
Benchmarks (hydra-node, tx-cost, --output-directory $(pwd)/../benchmarks)	3m 0s
Benchmarks (hydra-node, micro, -o $(pwd)/../benchmarks/ledger-bench.html)	1m 55s
Benchmarks (hydra-cluster, bench-e2e, datasets datasets/1-node.json datasets/3-nodes.json --outpu...	5m 21s
Benchmarks (plutus-merkle-tree, on-chain-cost, $(pwd)/../benchmarks)	1m 43s
Build specification using nix	59s
nix flake check	4m 34s
Publish benchmark results	0s
Publish test results	8s
Documentation	1m 19s
	39m 57s

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