community/step-cli: fix checksum
Error found on the 3.21 riscv64 builder.
>>> step-cli: Fetching step-cli-0.28.2.tar.gz::https://github.com/smallstep/cli/archive/refs/tags/v0.28.2.tar.gz
Connecting to github.com (140.82.121.4:443)
Connecting to codeload.github.com (140.82.121.9:443)
saving to '/var/cache/distfiles/v3.21/step-cli-0.28.2.tar.gz.part'
step-cli-0.28.2.tar. 1362k --:--:-- ETA
step-cli-0.28.2.tar. 100% |********************************| 1610k 0:00:00 ETA
'/var/cache/distfiles/v3.21/step-cli-0.28.2.tar.gz.part' saved
>>> step-cli: Fetching https://distfiles.alpinelinux.org/distfiles/v3.20/step-cli-0.28.2.tar.gz
>>> step-cli: Checking sha512sums...
step-cli-0.28.2.tar.gz: FAILED
sha512sum: WARNING: 1 of 1 computed checksums did NOT match