chore(deps): update docker.io/library/golang docker tag to v1.21.9 (v1.0) #6523

Job	Run time
Build tetragon	13m 9s
Test kernel 4.19-20231026.065108 / test group 0	18m 14s
Test kernel 5.10-20231026.065108 / test group 0	27m 32s
Test kernel 5.4-20231026.065108 / test group 0	23m 59s
Test kernel bpf-next-20231030.012704 / test group 0	15m 57s
Test kernel 6.1-20231026.065108 / test group 0	16m 46s
Test kernel 5.15-20231026.065108 / test group 0	24m 25s
post-test	3s
	2h 20m 5s

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