Added Dijkstra era #18229

Job	Run time
fourmolu	33s
build (9.6.7, ubuntu-latest)	34s
build (9.8.4, ubuntu-latest)	34s
build (9.10.2, ubuntu-latest)	29s
Check branch history	10s
gen-hie	33s
build (9.12.2, ubuntu-latest)	32s
cabal-format	7s
Check if formal-ledger-specifications SRP is valid	10s
codegen	1s
${{ matrix.package }}-${{ matrix.ghc }}-${{ matrix.os }}	1s
Tests completed	1s
Send a slack notification on \#ledger-internal if the nightly build failed	1s
	3m 46s

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