chore(deps): update docker.io/library/golang docker tag to v1.21.9 (v1.0) #6520

Job	Run time
Build tetragon	12m 53s
Test kernel 5.15-20231026.065108 / test group 0	25m 15s
Test kernel 4.19-20231026.065108 / test group 0	18m 12s
Test kernel 5.10-20231026.065108 / test group 0	27m 50s
Test kernel 6.1-20231026.065108 / test group 0	17m 40s
Test kernel 5.4-20231026.065108 / test group 0	25m 33s
Test kernel bpf-next-20231030.012704 / test group 0	16m 6s
post-test	3s
	2h 23m 32s

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