Update old github links #271

Job	Run time
t8code_w_shipped_submodules_tests / t8code_cmake_tests	4m 1s
preparation (OFF) / cmake_preparation	1m 13s
preparation (ON) / cmake_preparation	1m 16s
t8code_linkage_tests (OFF, Debug) / t8code_cmake_tests	7m 40s
t8code_linkage_tests (OFF, Release) / t8code_cmake_tests	6m 44s
sc_p4est_tests (OFF) / sc_p4est_cmake_tests	3m 47s
sc_p4est_tests (ON) / sc_p4est_cmake_tests	3m 1s
t8code_tests (OFF, Debug) / t8code_cmake_tests	2m 54s
t8code_linkage_tests (ON, Debug) / t8code_cmake_tests	10m 7s
t8code_linkage_tests (ON, Release) / t8code_cmake_tests	7m 28s
t8code_tests (OFF, Release) / t8code_cmake_tests	2m 35s
t8code_tests (ON, Debug) / t8code_cmake_tests	3m 52s
t8code_tests (ON, Release) / t8code_cmake_tests	2m 56s
	57m 34s

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