[ change ] Deprecate Agda-2.6.3 because it does not build with GHC 9.… #70

Job	Run time
build-and-test (macos-latest, Agda-2.6.4.3)	39m 52s
build-and-test (ubuntu-latest, Agda-2.6.4.3)	37m 2s
build-and-test (windows-latest, Agda-2.6.4.3)	40m 52s
build-and-test (macos-13, Agda-2.7.0.1)	1h 6m 41s
build-and-test (windows-latest, Agda-2.7.0.1)	38m 21s
build-and-test (ubuntu-latest, Agda-2.7.0.1)	34m 0s
build-and-test (macos-13, Agda-2.6.4.3)	1h 8m 3s
build-and-test (macos-latest, Agda-2.7.0.1)	32m 28s
	5h 57m 19s

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